Nine-year-old Adam has learned a new way to eat—and so have the other members of his family. Fried potato chips have been banished from the kitchen shelves in Adam’s home in Newton, a leafy Boston suburb. French fries are not on the family menu either. Pizza, when it’s served, is often homemade on small loaves of whole wheat pita bread. All of these staples of the modern American diet used to be among Adam’s favorites, but he eats them now only as an occasional treat.

For breakfast on a recent morning, Adam—a friendly, articulate boy with striking gray-green eyes—had a bowl of high-fiber cereal with milk and a big bowl of mixed fruit: grapes, blueberries, melon, strawberries, and cantaloupe. On other days he eats a cooked egg white with low-fat cheese on an English muffin, or lox and light cream cheese on half a bagel. The lunch he carries to school typically includes a peanut butter sandwich, fruit, yogurt, and skim milk. He often snacks on high-fiber, low-fat health bars or cucumber pickles—and he drinks plenty

of water. Adam does not consider his new pattern of food choices a “diet.” He calls it an eating plan, or a healthier way to eat. When I visited Adam’s home one spring afternoon, he had been following it for almost a year. His parents and his 5-year-old brother were eating according to the plan, too. “I’ve been doing really well on it, and I’m going to keep it up,” he said.

Adam learned about the eating plan at Optimum Weight for Life, or OWL, a research and treatment program for overweight children directed by David Ludwig, a Harvard pediatrician and obesity researcher at Boston’s Children’s Hospital. OWL is based on a growing body of research by Ludwig and others suggesting that a diet rich in fruits and vegetables but low in refined starches and sugars, and which also contains protein, unprocessed whole grains, some dairy products, and a moderate amount of fat, may be healthy for the heart and least conducive to weight gain and diabetes. In the medical literature, such an eating plan is called a low-glycemic-index diet.

Adam’s mother, Laura, knew by the time her son was 8 that he would need to learn to manage his weight. As an adult, she had experienced her own weight problems and had joined Weight Watchers to revise her eating habits. Adam’s father had also struggled intermittently with weight gain. At 8, Adam was big for his age and, as his mother put it, “a good eater”—in fact, he seemed to be hungry all the time. A picture taken that summer shows a round-faced, chubby child. The family’s pediatrician, concerned that the boy was unhealthily heavy, referred Adam to OWL, which treats overweight kids 4 and older. After

Adam underwent an initial medical evaluation, he and his parents attended group sessions to learn about the new eating plan. He returned to the OWL clinic for follow-up visits about every two months. Adam remembers watching a slide show that taught him the basics of the plan while his parents learned how it is thought to work. Starchy foods like potatoes or bread made from white flour are rapidly broken down to sugar by the body, tending to raise blood sugar levels rapidly and trigger a corresponding surge in insulin. A few fruits—bananas and watermelon, for instance—also cause a quick surge in blood sugar. Such foods are said to have a high glycemic index. (“Glycemic” is a medical term that means “putting sugar into the blood.”) On the other

hand, protein and fat, as well as most fruits and vegetables, which are high in fiber, take longer to digest so they raise blood sugar more gradually and do not provoke such a large or sudden insulin surge. Hence, they have a low glycemic index.

Whole grains that have not undergone much grinding or processing are also digested slowly, but the same whole grain can turn into a food with a high glycemic index if it has been finely milled. (For example, highly processed “instant” oatmeal has a high glycemic index, while relatively intact, slow-cooking “steel-cut” oatmeal has a low one.) In addition, including some fat as part of a meal slows the emptying of the stomach, so that nutrients are not delivered too rapidly to the intestines, where digestion and absorption into the bloodstream take place. Studies by Ludwig and his research team have found that children who were given a breakfast containing foods with a low glycemic index were less hungry during the day, and consumed fewer calories, than those who ate a breakfast containing an equal number of calories but composed of high-glycemic-index foods.

To Laura, part of the appeal of the OWL program was that its research suggested that while following the plan Adam would be less eager for snacks between meals—although healthy snacks are permitted in moderation. The insulin surge triggered by foods with a high glycemic index produces a corresponding plunge in the blood sugar level a few hours later. When blood sugar drops too low, there is a compensatory rise in other hormones, including the “stress” hormones epinephrine and cortisol, and hunger kicks in. In Ludwig’s studies, children and adults given low-glycemic-index diets have smaller ups and downs in blood sugar and lower insulin levels than those following a conventional low-fat diet, and they report less hunger. Laura also liked the plan’s flexibility. “What I think works about it is, it doesn’t say ‘You can’t have’ and ‘You can have,’” she observes. “It tries to say ‘More of this, less of that.’ You keep foods in proportion.”

Following the plan required big changes in Adam’s eating habits. His family had always eaten salad or vegetables with dinner, but Adam loved junk food, his mother says. Potatoes, especially French fries, were also a particular favorite, but they have an especially high glycemic index. “At the start, it was just so hard for me,” Adam recalls. At one

point “I said, ‘I can’t do this,’ and I almost stopped. But my mom and dad encouraged me to go back [to the plan] again.” A year into the plan, Adam says he has gotten used to it and no longer finds it difficult to follow. “It’s one of the easiest things I do,” he remarks. “It’s just part of my regular schedule. I don’t sneak treats at school or anything.”

The family’s shopping and cooking habits have also changed. They eat many more fruits and vegetables. Laura often grills or broils fish and, if she fries food, she uses olive oil. She routinely packs lunches at home rather than allow her children to buy lunch at school. She limits calories and fat in the family pantry by buying low-calorie bread, lean meats, and light margarine. She also invents recipes. “She made up a new fajita that’s yummy,” Adam says proudly.

For Adam’s family, switching to the plan wasn’t easy. Adam’s little brother is a picky eater and sometimes complains about missing the snack foods his mother no longer buys. “Our food bills are high,” says Laura. “To eat healthy is very expensive.” She estimates that she spends $100 more each week at the grocery store than her friends do, but also notes that she does save money by making three lunches a day instead of paying for them at school or work.

The results have been worth it. At 9, Adam looks like a different child. He weighs 34 pounds less now than he did last year, even though he’s been growing. He is slender and muscular. “I’m faster. I’m just much stronger now,” he says. He joined a swim team at the Newton YMCA and won a medal in the winter at the district championships. In the spring he joined a baseball team. Says Laura, “I think one of the reasons Adam never liked soccer was that it was too hard. He had trouble keeping up with the kids. Now he can. He can do what everybody else does.”

Adam still visits the OWL clinic for periodic checkups. “I’m not exactly trying to lose weight,” he says. “I’m just trying to stay on the plan and keep going.” According to his mother, “He knows what he can eat and what he can’t eat. It works for him. I really feel that if he learns that now, it’s a lesson that he can take through his life and always come back to.”

Following a low-glycemic-index eating plan like the one taught at the Boston OWL clinic is not the single “right” way for a child or a family to learn to eat healthily. In fact, despite the popularity of weight-loss regimens such as the South Beach Diet that are founded on similar concepts, most nutrition experts concur that diets based on foods’ glycemic index still need additional study, especially in large clinical trials designed to test their long-term effects on body weight and overall health. Nevertheless, the OWL plan’s emphasis on eating plenty of fresh fruits and vegetables, whole grains, and nonfat or low-fat dairy products while including sources of “healthy” fats such as olive oil, nuts, and fish are principles that most nutrition scientists and dietitians heartily endorse. Most American families could probably benefit from some of the lessons about healthy eating that Adam and his family have learned.

In today’s environment, parents can no longer take for granted that their children will grow up knowing how to make good food choices and maintain a desirable weight. The pervasive changes in our daily patterns of eating and activity make excess weight gain likely for just about everyone, at least at some time. Simply following one’s urges regarding food and exercise probably will not work for most people. Teaching children to make choices that add up to a healthy lifestyle requires a degree of sophistication that simply was not necessary for parents in the past. “If the environment were not the way it is, it probably wouldn’t matter if people had good parenting skills around food and physical activity,” notes Shiriki K. Kumanyika, a professor of epidemiology at the University of Pennsylvania School of Medicine. But today’s kids are far more sedentary than children were in past decades, and they live in an environment replete with high-calorie, tasty, heavily advertised food and drink. “We need to reeducate parents,” Kumanyika says. “As a nutritionist, when I look at what people think they should feed their kids, they haven’t a clue.”

Parents have a limited number of influential years in which to teach their children good eating habits and instill attitudes about exercise and lifestyle that their offspring will need all their lives. Although many experts believe that major environmental changes would be the most effective way to reverse the obesity epidemic in the United States and

elsewhere, no one is optimistic that such changes will happen rapidly—and they may not happen at all. In the meantime, one way to prevent obesity is to make parents more effective at “immunizing” their children against unhealthy weight gain. “It is not likely that we will ever return the environment to one in which … cognitive control of body weight is not required,” predicts researcher James O. Hill, director of the University of Colorado’s Center for Human Nutrition, in a recent article. “We should consider how to make sure that everyone has the information and tools needed to cognitively maintain energy balance.”

A few striking statistics help to sketch a portrait of the calorie-laden dietary environment that is pushing Americans’ weight steadily up the scale. The amount of food available to the U.S. population increased by 15 percent between 1970 and 1994, from 3,300 calories per person per day to 3,800. These figures don’t mean Americans are eating that whopping number of daily calories, since they include food that spoils, is wasted, or is discarded, but they do show that our country’s farms and food manufacturers are producing and marketing more food and drink than ever before—and they suggest that people have probably increased their caloric intake in response. A recent national survey indicates that American adults are indeed eating more than in the past. In the years 1999 and 2000, women were eating an average of 335 calories more per day than they ate during the early 1970s, and men were eating an average of 168 more calories per day. (The average daily caloric intake for women in 1999–2000 was 1,877 calories; for men, it was 2,618 calories.) These counts are based on 24-hour dietary recall data gathered from a national sample of people aged 20 to 74, as part of the government’s periodic National Health and Nutrition Examination Surveys (NHANES), a series of large national studies conducted by the U.S. Department of Health and Human Services.

Obtaining accurate information about what people eat can be difficult, because people tend to underreport their intake or even lie about it, and many survey participants understandably have difficulty remembering every item on the previous day’s menu. As a result, surveys by different government agencies sometimes obtain conflicting results. For example, in consecutive surveys by the U.S. Department of Agri-

culture (USDA), respondents reported consuming 7 percent fewer calories, on average, in 1994 than in 1978, and dietary data from the 1987 and 1992 National Health Interview Surveys also showed a modest decline in reported intake. However, the NHANES have consistently documented a gradual but steady increase in adults’ reported intake over the past three decades. These findings, combined with data on food production and other evidence from a variety of smaller studies, point toward the conclusion that Americans are consuming more calories.

Among U.S. children the findings of various surveys tell a more consistent story: they show that children’s average daily food intake has increased during the past quarter-century and even climbed slightly between the early and mid-1990s. Although underreporting of intake can affect the accuracy of data in children just as it can in adults, these cross-sectional studies—“snapshots” of dietary intake at different points in time—do suggest that today’s children are eating more calories now than a decade or two ago.

Where are those calories coming from? Again, information from survey participants about what Americans are eating may appear, at first glance, to be at odds with food production figures. Consider fat intake. Population surveys show that Americans reduced their fat intake between 1970 and 1994, from 42 percent of daily calories down to 38 percent. They may have done so partly in response to federal dietary guidelines issued in the early 1990s, which recommended that total fat should make up no more than 30 percent of the diet and saturated fat no more than 10 percent. Yet fat production per capita in the United States actually increased during that period, again suggesting that the survey findings might not accurately reflect everything people eat. An intriguing possible explanation for these seemingly contradictory findings is that even though fat makes up a lower percentage of the average person’s diet today than in 1970, American adults and children are eating more total calories—so their absolute daily intake of fat has actually risen. One analysis of children’s intake concluded that although fat as a percentage of kids’ diet fell from 38 percent to 32 percent between the early 1970s and the late 1990s, the actual amount of fat the average child eats each day has not declined because today’s children are eating more calories than the children of three decades ago.

Today’s children and adults drink far less milk than Americans did in past decades. Per capita milk consumption fell from 31 gallons in 1970 to 24 gallons by 1997. Milk consumption decreased by 37 percent in adolescent boys and by 30 percent in adolescent girls between the mid-1970s and the mid-1990s. Over the same period, soft drink consumption rose more dramatically than any other food category, suggesting that soda was replacing milk in the diets of many children and adults. By 1997 Americans were drinking 44.4 gallons of soft drinks per person per year, 10 gallons per person more than in 1987. Some children in the United States are introduced to soda before they reach their first birthday. By the age of 14, one-third of girls and more than half of boys are drinking three or more 8-ounce servings of soft drinks per day. This huge increase in soft drink consumption has helped boost Americans’ intake of added sugars to about double the maximum level recommended by federal dietary guidelines. Added sugars, especially from soft drinks, currently make up 16 percent of Americans’ total calorie intake—and 20 percent of the calorie intake of adolescents. Fructose, a major sweetener in soft drinks—and in many other products—is a sugar that does not trigger the same hormonal responses in the body as glucose, although it is chemically similar and contains the same number of calories per gram. Some experts have suggested that its increasing use in food and drink products since 1970 (when it was first marketed in the form of a sweetener called high-fructose corn syrup) may have played a role in the genesis of the obesity epidemic.

There is some evidence that high soft drink consumption may reduce children’s intake of important nutrients from other sources, including calcium, phosphorus, and various vitamins. Epidemiological research in children has linked soft drink consumption with higher total daily calorie intake and increased risk of obesity. Those findings apply not just to sodas but also to fruit drinks that contain a small percentage of fruit juice diluted by a large volume of sugary water. Researchers conducting the Nurses’ Health Study, a large, ongoing epidemiological study of U.S. women, recently reported that women who increased their consumption of sugar-sweetened soft drinks or fruit punch (from less than one drink a week to one or more drinks a day) gained significantly more weight over a four-year period than women

who held their intake constant or reduced it. The same study also showed that high intake of sugar-sweetened soft drinks or fruit punch (consuming one such drink or more per day) is associated with an increased risk of diabetes, compared with the risk seen in women who consume such drinks infrequently (less than one drink per month).

Not all dairy consumption is down. As milk fell, cheese rose. Between 1970 and 1997 annual cheese consumption increased from 11 to 28 pounds per capita. Much of that increase may have been propelled by an explosion in the popularity of pizza, a food high in total and saturated fat whose consumption increased 150 percent between 1977 and 1994. Pizza, along with pasta, soft drinks, and Mexican food, also has contributed to the rise in children’s daily calorie intake from carbohydrates—sugars and starches—during the past two decades. (Carbohydrates, fat, and protein as dietary calorie sources are discussed in detail later in this chapter.)

Meanwhile, Americans’ intake of fruits and vegetables has risen since 1970 but not to the minimum levels recommended by the government’s dietary guidelines, despite a federally financed advertising campaign to boost intake. In 1996 Americans ate an average of 1.3 servings of fruit per day, compared with 2 to 4 servings recommended in the guidelines, and they ate 3.8 servings of vegetables, compared with the recommended 3 to 5 servings. (According to the guidelines, examples of a serving are a single piece of fruit, 1 cup of raw leafy vegetables, or half a cup of chopped or cooked vegetables.) National dietary survey data collected between 1994 and 1996 reveal that children ate an average of 4.1 servings of fruits and vegetables daily, compared with the 5 recommended. Although these figures don’t seem too far off-target, the picture is less encouraging when intake is examined in more detail. Children’s average fruit intake, 1.4 servings per day, is below the minimum 2 servings per day recommended. French fried potatoes account for 46 percent of vegetable servings for children between the ages of 2 and 19, according to government data collected in 1999–2000. If potatoes were removed from the “vegetable” category, as some nutrition experts have advocated, children’s vegetable intake would be much farther below the recommended target level. In con-

trast, dark green and orange vegetables, which are especially rich in vitamins, made up only 8 percent of kids’ vegetable intake.

Indeed, despite the wide variety of fresh produce available in the United States, Americans of all ages tend to limit their consumption to just a few types. In 2000, five vegetables—iceberg lettuce, frozen potatoes, fresh potatoes, potato chips, and canned tomatoes—made up almost half of total vegetable servings, while orange juice, bananas, apple juice, apples, grapes, and watermelon accounted for half of all fruit servings.

Moreover, recent decades have seen a dramatic change in where our meals come from. A shift away from preparing food at home has been a major contributor to many of the alterations in the average American’s diet, affecting not only the sources of calories but, perhaps even more important, the “portion size,” or amount of a food or drink a person consumes during a meal or snack. This shift results from a variety of social and economic factors, including the high proportion of women who work, the growing complexity of family schedules, and the time demands of food shopping and cooking. Consumption of meals and snacks at fast food restaurants tripled between 1977 and 1995. By 1998, 21 percent of American households ate some form of take-out or delivered food on any given day. In 1997 nearly half of family expenditures for food were spent on food and drink prepared outside the home, and more than one-third were for fast food. By the mid-1990s, consumption of foods prepared away from home made up almost a third of children’s total calorie intake. Both take-out and restaurant food tend to be higher in fat and calories than food cooked at home. Studies in teenagers and adults link frequent consumption of fast food with higher daily calorie intakes and higher body weights. A recent study found that teenagers served a fast food lunch ate an average of 1,652 calories during that single meal, more than 60 percent of their estimated daily energy requirement! Although all the kids in the study tended to overconsume fast food, overweight teens ate more than lean ones and were less likely to compensate by eating less at other meals during the day.

In addition, foods are being sold in increasingly larger portion sizes, a trend that has been under way for decades. A “portion” and a

“serving” are not the same thing. A serving is a standard amount used to advise people about how much to eat or to specify the calorie and nutrient content of different foods. For example, in the federal government’s dietary guidelines and Food Guide Pyramid, a serving of bread is a single slice and a serving of milk or yogurt is 1 cup. A portion, in contrast, is the amount of food placed on the plate or dispensed in a single-use container. The heaping portion of spaghetti customers often eat in Italian restaurants might amount to 4, 5, 6, or more pasta servings (defined as a half cup of cooked pasta). The recent expansion in the nation’s portion sizes started as a marketing strategy by food manufacturers and the restaurant industry, but there is evidence that over time it has transformed Americans’ cooking and eating behavior at home.

The amazing growth of the Coca-Cola container is a good illustration of the “supersizing” marketing trend. A bottle of Coca-Cola in 1916 held 6.5 ounces. By 1950, 10- and 12-ounce “king-sized” bottles were on the market, but the 6.5-ounce bottle was still the best-seller. Today, a regular can of Coca-Cola holds 12 ounces, 20-ounce bottles have become standard in many vending machines, and 32-ounce bottles are widely sold. Similar supersizing trends have occurred for fast food sandwiches, burgers, portions of French fries, bagels, popcorn, candy, and other products. The ballooning of portion sizes is reflected on grocery store shelves and even in cookbook recipes; researchers have documented it in almost every food category.

The hefty sizes are popular with consumers, who figure that larger-volume products are a better deal, and they are profitable for producers. But supersizing food portions trains people to overconsume. Often, the fine print on government-required food labels reveals that a bottle of sweetened fruit drink or a bag of chips contains several servings, yet the packaging and advertising for supersized products are designed to encourage the purchaser to eat or drink the whole thing. Research suggests that the supersizing of food portions adversely affects people’s unconscious decisions about how much food to consume at one time and is directly correlated with Americans’ increased calorie intake. In a fascinating series of studies involving foods as varied as chips, submarine sandwiches, and baked pasta, nutrition researcher Barbara J. Rolls

of Pennsylvania State University has shown that the larger the portion, the more people eat—even though fewer than half of participants report noticing differences in the portion sizes they are served.

To find out whether young children respond in the same way, Rolls and her colleagues conducted a study in which children were served varying amounts of macaroni and cheese. The researchers found that 3-year-old children tended to eat the same amount regardless of portion size, but 5-year-olds ate larger amounts when given larger portions—suggesting that as children grow older, they become responsive to environmental cues that tend to override their body’s internal satiety signals. In another study of preschool children, Rolls and colleagues found that when they doubled the size of an entree served at lunch, children increased the average size of each bite they took and as a result ate 25 percent more of it.

Prominent among the environmental stimuli that influence food choices and intake is ubiquitous food advertising. Food manufacturers, retailers, and services are second only to the automobile industry in money spent on advertising. Food and beverage advertisers spend an estimated $10 billion to $12 billion annually to promote their products to children and adolescents. A report released by the Kaiser Family Foundation in 2004 found that the typical American child sees about 40,000 advertisements per year on television and that the majority of TV ads targeting children are for candy, soda, and fast food. One study found that television commercials influence the food preferences of children as young as 3 to 5 years old.

In the U.S. population as a whole, foods that are most heavily advertised (snacks, candies, convenience foods, soft drinks, alcoholic beverages) are overconsumed relative to what is recommended in national dietary guidelines, while the least advertised foods, such as fruits and vegetables, are underconsumed. Although the U.S. Department of Agriculture spent about $1 million in 1999 to promote its “5 A Day” message encouraging people to eat more fruits and vegetables, the majority of Americans consume less. By comparison, McDonald’s spent almost $572 million and Burger King $407 million on advertising in 1998.

“The entire culture has moved, in my view, in a direction that seems to be the worst direction if you’re concerned about developing

obesity,” says researcher Michael Schwartz of the University of Washington. “If you wanted to see what is the environment that would maximize the rate of weight gain—we’ve more or less created it.”

Faced with an environment packed with tasty, fattening foods and resounding with cues urging us to eat more of them, what can parents and other adults do to teach children to resist these seemingly irresistible forces? The good news is that, on an individual or a family level, the changes in behavior required to avoid weight gain may be less drastic than one might expect. Simply by making small changes in daily routines and in the home environment, parents have more power than they may think to improve the family diet and move their own habits and those of their children in a direction that can help everyone to achieve or maintain a healthy weight. University of Colorado’s James Hill estimates that the “energy gap” causing so many children and adults to gradually gain weight probably amounts to an average of 100 calories per day—that is, on average, people are likely consuming about 100 calories more than they expend in activity. That’s equivalent to about one slice of bread or two-thirds of a can of soda. Since excess caloric intake is stored with only about 50 percent efficiency, such an imbalance in energy intake would lead to about 50 extra calories being stored as fat—enough to account for the average weight gain of about 2 pounds per year seen in U.S. adults between the ages of 20 and 40.

It should be possible for many people to eat 100 fewer calories a day without drastically altering their lifestyle, Hill suggests. For instance, eating three bites less of a typical fast food hamburger could reduce intake by 100 calories. Moderately increasing daily activity would also help to close the gap, probably at least preventing further weight gain. Walking an extra mile each day, about 2,000 to 2,500 extra steps, would burn 100 calories. Because children do not inherently know how to make such choices, Hill writes, “as a society, we should be more willing … to carefully manage the food and physical activity environments of our children at home, in school, and in other places.”

A diet high in fat and highly processed carbohydrates is probably the kind most likely to promote weight gain, yet this is the way most Americans eat, notes Michael Schwartz. He believes that parents can do a lot to prevent obesity in children by teaching them to be aware of

their food choices and to make physical activity a habit. “As a parent, my personal feeling is, if people were as conditioned to exercise every day as they are to brush their teeth, I think that would go a long way,” he says. In time, changes that start with individuals and families might lead to a shift in the norms of an entire society.

People often complain about what they view as conflicting dietary advice from experts and inconsistent findings from scientific studies about nutrition, yet in many broad areas there is little or no disagreement. Experts on nutrition and obesity are virtually unanimous about a number of steps parents and other adults can take to improve the chances that the children they love will grow up with healthy eating habits.

As often as possible, meals should be a family activity, a time for parents and children to be together. Starting in infancy (discussed in Chapter 6), children should be able to see the face of the person feeding them. Just as a baby should never be put to bed with a bottle or propped in a seat with one, older children should generally not be expected to eat meals alone. It’s also wise to limit eating and drinking to areas of the home such as the kitchen or dining room, since children become conditioned to expect food in physical settings where it is usually offered. In particular, parents should not allow children to eat—even snacks—while watching television. As I explain in the next chapter, there is ample research evidence that television viewing contributes in multiple ways to the epidemic of childhood obesity, and one of those ways is a tendency for kids to ingest excess calories almost unconsciously while watching TV.

Children generally do best with regularly scheduled meals each day—especially breakfast, which has been shown to improve their thinking skills as well as academic and physical performance. Recent studies in children and adults have also found that those who eat breakfast regularly are less likely to be overweight. It also appears that there is nothing magic about a three-meals-a-day schedule: one study found that adults who ate frequent small meals (four or more daily) were less likely to be obese than people who ate three large ones.

In addition to regular meals, many children, especially preschoolers and fast-growing adolescents, need snacks. However, significantly more U.S. children report consuming snacks today than in the 1970s, and this increased snacking has probably contributed to the rise in kids’ calorie intake. Steering kids toward snacks that are not calorie dense, such as fresh fruits, vegetables, and nonfat or low-fat dairy products, can improve their diets and help limit excessive caloric intake.

Meals and snacks should not be rushed; eating at a leisurely pace allows time for the digestive tract and the brain to sense satiety and signal that it’s time to stop. Some research on infants suggests that very rapid intake of calories is associated with excess weight gain and may lead to increased obesity risk. Slower ingestion of calories may be one reason why breast-fed babies have a lower risk of later obesity than bottle-fed ones. Eating out or picking up a take-out dinner is a convenience that few families will want to forgo entirely, but parents and others concerned about preventing obesity should resist the societal trend toward relying ever more heavily on restaurant or take-out food. A study of children and older adolescents found that those who ate dinner at home with their families consumed fewer fried foods (both at home and elsewhere) and less soda, and ate more fruits and vegetables, than those who did not.

Preparing a meal at home allows those who cook it to control the kinds of fats used (if any), the sugar and salt content, and whether foods are steamed, baked, boiled, grilled, or fried. It is difficult and sometimes impossible for consumers to influence what goes into a meal cooked in a restaurant or into a frozen entree or heat-and-serve item from the deli or supermarket. Sharing meal preparation with children also teaches them lifelong lessons about how to choose healthy foods and how to handle food safely, as well as imparting cooking skills and family and cultural traditions.

Although eating with the family is good for kids, highly charged emotional struggles focusing on food are not. Research has shown that absolute bans on certain foods are likely, paradoxically, to make children crave them more: telling a child “no French fries” is a surefire strategy for making them a favorite. Conversely, insisting that a child eat broccoli may trigger a fixed opposition to that vegetable. Parents

can have a more positive impact by letting the child see them eating and enjoying the food they wish to promote (such as a cooked vegetable) and by encouraging the child to try a taste, even a tiny one, each time it is served. It’s normal and expected for young children to distrust or reject an unfamiliar food, and research has shown that it may take 5 to 10 experiences with a new item before some children accept it. “Absolutely, repeated introductions do help a child get used to foods,” says William Dietz of the CDC. “I think it’s reasonable to suggest to a child that they have a bite of something.”

Sheila Crye teaches after-school and summertime cooking classes to children between the ages of 9 and 14 at her home in a Washington, D.C., suburb. The parents of some of her students complain that their kids have been picky eaters all their lives. One boy wanted to become a chef but was unwilling to try the new dishes he was learning to make. “He’d look at something and he wouldn’t even want to taste it,” Crye recalls.

In an older child such reluctance may occasionally stem from an early unpleasant experience with a bad-tasting medicine or from a parent’s ill-advised practice of putting peppery sauce on a child’s tongue as a punishment (“saucing”). But many kids are simply cautious by nature and are slow to accept things that look, smell, and taste unfamiliar. Crye persuades her students to promise to taste what they cook. She tries to provide fresh ingredients whenever possible, believing that they make foods taste best. “It’s a trust relationship,” she says. She promises her students, “I’m going to help you fix things that you will like. I’m not going to make you eat anything really nasty.” Because picky eaters will sometimes try to avoid tasting a new food by swallowing a bite as quickly as possible, she asks them to describe the flavor: “Is it salty? Is it sweet? Can you tell what spices are in it?” Crye tells parents: “Keep serving things that are normal, good foods. Make them take a taste. You don’t have to fight about it. If you can get a commitment from them that they will take the taste, that’s best.”

Urging children to clean their plates, to finish every last morsel, can interfere with their developing ability to sense satiation, the feeling that makes a person end a meal. In a study comparing two groups of children, those who were taught to focus on noticing the sensation of

fullness in their stomachs did better at adjusting their intake in response to foods’ calorie density than the group rewarded for cleaning their plates. Children’s bodies have their own well-regulated systems for determining their caloric needs. Those needs may vary from day to day—much to the distress of parents who want to see a child eat three “good” meals daily—but research has shown that even picky toddlers eat an appropriate and consistent number of calories for their size when their intake is averaged over two or three days. When a baby refuses to eat another spoonful or when a child says he is full, parents should respect the child’s internal satiety signals. As soon as they are old enough to do so, children should be encouraged to determine their own portion sizes and serve themselves.

How else can parents and other adults best encourage healthy eating habits while avoiding battles over food? They can start by ensuring that the entire family is committed to having healthy foods in the home. The available choices, the menu at meals, and family policies about eating should be the same for everybody. Parents should not set a bad example by eating junk food or following an unbalanced fad diet while expecting their children to follow a different set of rules. Conversely, parents or other caregivers should not give in to the temptation to feed kids unhealthy items just because they are easy to prepare or because they know children will eat every bite. “It’s essential” that the whole family commit to following a healthy eating plan, says Harvard’s David Ludwig. “With overwhelming environmental influences to eat junk food and not get enough exercise, one has only the family. The family is the last bastion of defense against the toxic environment.”

Children need to be able to control how much they eat and whether or not they will eat specific foods, but adults should determine what the range of choices in the pantry will be and what products will not be on the home menu. That strategy will help prevent battles over whether a child can or cannot have a particular food. It also encourages kids to develop healthy tastes that will persist as they get older. “Parents should be in charge of what children are offered and when, and children should be responsible for the decision to consume what is offered or not,” write William Dietz of the CDC and Steven Gortmaker of the Harvard School of Public Health. “That division of

responsibility is crucial,” says Dietz. “Once the parents have made the offer, their responsibilities are over. If the child decides not to eat it, it’s not the obligation of the parent to provide an alternative—which is always the temptation.”

Parents whose child refuses to eat dinner may worry that the child will go to bed hungry. “I’d say, that’s just the point,” Dietz says. “Your child needs to learn the logical consequences of not eating. That’s a lesson that many children never learn.” Dietz believes that working parents who have limited time to spend with their kids may be tempted to give in to food demands because they think that having quality time with their children means avoiding an argument at any cost. “I think parents accede to their children’s wishes about food when children are not in a position to make responsible decisions about food,” he says, adding that, while there is no formal scientific evidence that the approach he advocates can reduce obesity, “it clearly reduces conflicts around feeding.”

What kinds of foods can be considered “healthy” options? What kinds of products should parents and others who care for children choose to stock the refrigerator and pantry in order to promote good nutrition? Here too there’s a good deal of agreement among nutrition experts. But before I offer specific suggestions, let’s consider some basic information about the three major sources of energy that make up a balanced diet.

Energy-providing nutrients in food fall into three major categories: carbohydrates, proteins, and fats. Carbohydrates are sugars, present either as small molecules like glucose, fructose, and sucrose (table sugar)—the ingredients that sweeten baked goods, candy, and soft drinks—or linked together into much larger molecules called starches (as in potatoes, bread, rice, and pasta). Proteins are long, chainlike molecules found in animal products (meat, eggs, fish, dairy foods) but also in some plant foods such as tofu, brown rice, and beans. Fats are oily substances found both in animal products (meat, chicken, fish, butter, milk) and in many plant foods (avocadoes, nuts, olives, coconuts). Some foods belong strictly to one category—for instance, most fruits provide all or almost all of their calories from carbohy-

drates, while olive oil is pure fat. Many foods contain nutrients belonging to more than one category.

Our bodies are also partly made of proteins, fats, and, to a lesser degree, carbohydrates. For example, some 10,000 different kinds of proteins—molecules made of smaller building blocks called amino acids—provide the structural scaffolding for all of our cells and tissues as well as the chemical machinery (in the form of enzymes, hormones, neurotransmitters, and other substances) that keeps us alive and conscious of our environment. Fat is the major ingredient in the membranes that enclose and protect our cells, and it forms the insulation that sheathes nerves in the brain, spinal cord, and elsewhere in the body, allowing them to transmit messages rapidly. Sugars are attached to some of our bodies’ important proteins and are sometimes found on the surfaces of our cells. For example, sugars are key components of the “blood group” proteins on the surfaces of red blood cells that determine whether a person’s blood is type A, B, AB, or O. Fat and sugars are also stored in body tissues as energy depots.

Much of the seemingly inexhaustible debate about diets reported in the media centers on what proportion of daily calories people should get from each of the three major nutrient categories. Perhaps the most frequent topic of dispute concerns the percentage that should be obtained from fat. A related controversy centers on carbohydrates, the nutrient category that provides the majority of calories in most people’s diets.

When the USDA’s familiar Food Guide Pyramid, a teaching tool developed to illustrate the government’s dietary guidelines, was first released in 1992, the average American got about 45 percent of daily calories from carbohydrates, about 40 percent from fat, and about 15 percent from protein. The dietary guidelines, at least since the early 1990s, have sought to reduce people’s fat intake and to replace some of the fat calories with calories obtained from carbohydrates. Carbohydrates formed the base of the Food Guide Pyramid, with grain-based foods such as breads, cereals, and pastas recommended to provide at least half of one’s daily calories. They also generally urged that fat intake be kept at no more than about 30 percent of daily calories. Protein made up the remaining 15 percent of daily caloric intake.

In the past decade or so, Americans have responded by reducing

the proportion of calories they obtain from fat to about 35 percent, on average. They have also shifted their eating patterns to include many more reduced-fat and fat-free products. Such products are not always low calorie; often they simply provide their calories in the form of sugar or other carbohydrates instead of fat. During the same period, an increasing proportion of the population has become overweight or obese.

Some nutrition experts have speculated about whether the federal guidelines and their graphic representation in the Food Guide Pyramid might have unintentionally contributed to rising obesity rates by prompting people to eat too many carbohydrates, especially highly processed or refined carbohydrates that are quickly digested to sugar in the body. The food industry, in response to the government’s recommendations, developed and marketed many new “low-fat” products that were high in such carbohydrates. The recent popularity of the Atkins and South Beach diets, weight-loss regimens that specify a relatively low percentage of calories from carbohydrates, has focused intense public attention on this nutrient category, making “low-carb” the latest marketing buzzword. Most dietitians would agree that cutting intake from some sources of carbohydrates—such as added sugars and highly processed starches, like those found in pastries, white bread, and pizza—would be healthy for many Americans. But carbohydrates from foods such as fruits, vegetables, whole grains, and beans should remain a healthy and fundamental part of a balanced diet.

The government’s dietary guidelines, which establish the direction for all government nutrition programs, are revised every five years. As this book went to press, the expert committee charged with proposing changes for the upcoming 2005 dietary guidelines issued its recommendations. Regarding carbohydrates, the expert panel urges Americans to increase their fruit and vegetable intake and to opt for foods that are rich in fiber—for example, by choosing whole grains rather than refined grains and whole fruits rather than juices. It also notes the evidence linking sugar-sweetened beverages and weight gain, and suggests that reducing intake of added sugars (especially sugar-sweetened beverages) may help people control their weight.

How much fat should be included in a healthy diet? Some nutrition experts, such as Walter Willett of Harvard Medical School, argue in favor of allowing a somewhat higher fat intake than the current guidelines suggest—up to about 35 percent of daily calories instead of 30 percent—but emphasize that most of the fats people eat should come from plant oils and seafood rather than animal sources, as in the so-called Mediterranean diet (traditional in coastal areas of Italy, Greece, and Spain). Citing epidemiological and clinical studies, Willett contends that eating a moderate amount of these “healthy” fats helps prevent heart disease by raising HDL (“good”) cholesterol. Willett and some of his colleagues have devised a food pyramid that reflects this advice.

The animal fat found in milk, butter, ice cream, cheese, and red meat is mostly of a type called saturated fat. Saturated fats are solid at room temperature; this property is related to the chemical structure of the carbon-chain molecules called fatty acids they are made of. In saturated fats, those carbon chains are maximally loaded with hydrogen atoms. A high intake of saturated fat raises the levels of total cholesterol, both LDL (nicknamed “bad” cholesterol because it can promote damage to arteries) and HDL (protective for arteries). On balance, a diet high in saturated fat increases the risk of chronic damage to the walls of arteries, a process that eventually causes narrowing of the blood vessels and leads to heart disease. Experts agree that Americans should limit their intake of saturated fats.

In contrast, unsaturated fats (both “monounsaturated” and “polyunsaturated”) contain fatty acids composed of carbon chains that don’t hold so many hydrogen atoms. These types of fats, which are liquid at room temperature, are the kind found in most vegetable oils, fish oil, and nuts. They are a healthier form of fat; in fact, research indicates that monounsaturated fats, especially, help protect against blood vessel damage. Both monounsaturated fats and polyunsaturated fats lower the blood level of “bad” LDL cholesterol and raise the level of “good” HDL cholesterol. There is widespread agreement that when possible the fats we eat should be monounsaturated or polyunsaturated. Especially healthy for the heart and blood vessels are the n-3 fatty acids, a class of polyunsaturated fatty acids found in fish, flaxseed and canola

oils, walnuts, and various other foods. In any case, total fat intake should remain low to moderate.

A third fat category, trans fats, contains substances developed by the food industry as a way to artificially solidify fats from vegetable oil, making them more convenient to use in some kinds of cooking and prolonging the shelf life of certain products. Trans fats are made by chemically attaching some hydrogen atoms to the unsaturated carbon chains that make up vegetable fats. It turns out that trans fats are probably even worse for the arteries than saturated fats, because they raise LDL cholesterol but do not raise HDL cholesterol. Experts agree that people should try to avoid trans fats, which are present in stick margarine, in many fried foods, and in countless processed foods, such as commercial baked goods like crackers, bread, and cookies. It has been difficult for consumers to find out whether a product contained trans fats, but the Food and Drug Administration (FDA) has ruled that food companies must list them on product labels by 2006. Some companies have already begun to list the trans fat content on their labels or to identify products containing no trans fats. Mention of “partially hydrogenated vegetable oil” on a food label is another clue that a product contains trans fats.

Nutrition expert David Katz of the Prevention Research Center at Yale suggests that the debate among researchers over what level of fat intake is desirable has made people lose sight of a much more important point: most Americans can improve their diet by both reducing total fat intake and shifting away from saturated and trans fats. Epidemiological studies point to health benefits from both the Mediterranean diet and a traditional Asian diet, which is lower in fat. Trials of low-fat diets for prevention of heart attacks and diabetes have found that such diets are effective for those purposes. “We’ve got good evidence that cutting fat and shifting to healthy fats are both potentially good things to do,” Katz says.

On the issue of dietary fat, the advisory panel for the government’s 2005 dietary guidelines urges Americans to keep their daily saturated fat intake below 10 percent of total calories, to keep trans fat intake below 1 percent of total calories, and to eat no more than 300 milligrams of cholesterol per day. (Eggs and organ meats are rich in choles-

terol; it is also present in the fat found in meat, shellfish, poultry, and dairy products.) The panel also suggests eating 2 servings of fish a week because the n-3 fatty acids found in fish can help prevent heart disease, although it recommends that children and pregnant or breastfeeding women should avoid fish with a high mercury content. For adults the panel states that total fat intakes ranging from 20 percent to 35 percent are recommended—reflecting the idea expressed by Katz that both

low-fat and moderate-fat diets can be acceptable, provided that the diet emphasizes “healthy” fats. However, very low fat diets are not recommended for children and adolescents. The panel recommends that children aged 2 to 3 years should get at least 30 percent of daily calories from fat and that children aged 4 to 18 should get at least 25 percent of calories from fat.

There is probably the least debate about protein, the third major source of nutrients in a balanced diet. A certain amount of daily protein in the diet is essential, since the human body cannot make all the amino acids it needs to stay alive and healthy. But the typical American diet contains ample protein for this purpose. Although the Atkins diet, a perennially popular short-term weight-loss diet, specifies a high percentage of calories from protein (as well as a low percentage from carbohydrates and a relatively high percentage from fat), many experts worry that eating a high-protein diet over a long period of time is potentially risky. It can cause calcium loss from the bones and places extra stress on the kidneys, which must excrete the waste compounds produced by digesting protein. (Following the Atkins diet for a long time is also likely to be hazardous for the heart and blood vessels, if people maintain a high total and saturated fat intake.)

All of this discussion about nutrient intake doesn’t mean you have to sit down and figure out exactly what percentage of your daily calories comes from fat, carbohydrates, and protein. Such precision isn’t necessary. An authoritative report on dietary intake was issued in 2002 by the Institute of Medicine. It reflects the current consensus among nutrition experts that various kinds of diets, including diets with a range of different intakes within the three major nutrient categories, can be healthy. Such a range reflects cultural variations in eating habits and recognizes that different individuals or families will prefer different foods. The report specifies that acceptable fat intakes can range from 20 percent to 35 percent of daily calories, carbohydrate intakes from 45 percent to 65 percent, and protein intakes from 10 percent to 35 percent. Anyone who sticks to the general eating principles about which there is broad agreement—emphasizing fruits and vegetables, whole grains and fiber, limiting foods with added sugars, and limiting total fat, especially unhealthy saturated or trans fats—should be able to eat a healthy diet.

Reducing or eliminating certain foods from the home still leaves ample room for variety. For example, parents can change their household shopping and cooking practices to limit red meats high in saturated fat, to include more fish, poultry, and vegetarian dishes, and to grill, bake, or steam foods instead of frying them. For snacks, children should be offered a choice, but everything on the list should be healthy: for example, fresh fruit, carrot sticks, dry-roasted nuts, whole wheat crackers with low-fat cheese, baked potato chips, raisins, low-fat yogurt, baked pretzels. Examples of items to be removed from kitchen shelves (and hence not available as a focus of conflict) might be fried chips, candy, and high-fat baked goods. If parents make a point of not buying calorie-dense sweets and snack foods loaded with unhealthy saturated or trans fats, children will not expect to eat them at home and will be more likely to develop a liking for healthier alternatives. Providing what David Katz calls “a safe nutritional environment” requires parents to become expert shoppers and label readers. “Know what to choose,” he says. “If your kids want chips, you have chips. If they want cookies, you have cookies. But it’s the best product in every category.”

Many experts recommend that parents banish regular sodas and sugared drinks (such as fruit punch or fruit drinks containing a low percentage of fruit juice) from the household since they are a major source of “added sugars” in the diet unaccompanied by more valuable vitamins or nutrients. Although such drinks are high calorie, research suggests they do not trigger a corresponding sense of satiety, so drinking large quantities of them can greatly boost daily calorie intake.

Children, like adults, should be encouraged to drink water instead of sweetened beverages when they are thirsty. Many people tend to confuse thirst with hunger and reach for a soda when a glass of water is all they need. Keeping the body well hydrated is good for the kidneys, digestive tract, circulatory system, and brain, but drinking beverages that contain a lot of added sugar and minerals isn’t really necessary, except perhaps for people who have been burning a great deal of energy or losing lots of sodium or potassium because of vigorous exercise or very hot weather. Teaching children to quench their

thirst with water instead of with soft drinks and juices would go a long way toward reducing the calorie excess that is contributing to the obesity epidemic.

Milk is an important source of calcium for children, but kids older than 2 don’t need whole milk. In fact, the only age group in America for whom whole milk is still considered healthy is children between 1 and 2 years old, because their brains are growing rapidly, and fat is the major ingredient in nerve cell membranes and the myelin that insulates nerves. On the other hand, infants under the age of 1 should receive breast milk or infant formula rather than cow’s milk, because of concerns about links between early exposure to the proteins in cow’s milk and allergies or other health problems.

Whole milk is almost 4 percent fat, which may not sound very high, but consider that about half the calories in whole milk come from fat, much of it the unhealthy saturated variety. For everyone over the age of 2, fat-free (skim) milk or milk that is 1 percent fat is a better choice. Similarly, choosing fat-free or low-fat yogurt, cheese, and cottage cheese will help limit saturated fat intake.

Two to three servings of dairy products per day for children and adults are recommended by current federal dietary guidelines. (Examples of a serving are a cup of milk or yogurt or an ounce and a half of low-fat cheese.) However, the advisory panel for the upcoming 2005 dietary guidelines recommends that adults and children should have approximately 3 cups daily of fat-free or low-fat milk or an equivalent amount of other nonfat or low-fat dairy products, particularly because of evidence that this level of dairy consumption can prevent low bone mass and osteoporosis in later life. Some epidemiological studies suggest that diets high in total calcium and dairy consumption may be associated with a reduced risk of obesity in children and adults. In a limited number of studies, dairy consumption has also been linked with a reduced risk of developing insulin resistance and the metabolic syndrome. Further research is needed to confirm these findings and to seek the explanations for them. For example, in some studies of children, higher dairy intake is associated with lower soda intake, a factor that might account for the observed reduction in obesity risk. On the other hand, laboratory studies in animals suggest that dietary calcium

may play a role in fat cell metabolism, reducing the tendency to store fat and aiding in regulation of body weight. In addition, eating nonfat or low-fat dairy products may be associated with a reduced risk of obesity and of insulin resistance for other reasons besides calcium—for example, because such foods have a low glycemic index or because they may enhance satiety.

Some nutrition experts are skeptical of findings suggesting a link between dairy consumption and weight control, pointing out that much of the research has been funded by the dairy industry. A recent review of the evidence urges that large clinical trials be carried out in overweight adults to find out whether diets high in dairy products or total calcium can help people attain a healthier weight. Evidence from other epidemiological studies suggests that diets high in dairy products may be associated with a small increase in the risk in later life of prostate cancer (a common cancer in older men) and ovarian cancer (a rare one in women). Since studies exploring these possible associations have yielded inconsistent results, further research is needed to determine whether they are meaningful. On balance, milk and other dairy foods provide valuable nutrients and help build and maintain bone strength. It makes sense for children and adults to include them in their diet as long they are careful to choose fat-free or low-fat products.

Not everyone can digest dairy products easily. Babies, of course, are engineered to digest everything in breast milk, and most young children can digest cow’s milk, although some are allergic to certain proteins in it. However, many teens and adults have trouble digesting dairy foods because their bodies make reduced quantities of the enzyme lactase, which breaks down lactose, the major sugar in milk. People with reduced lactase levels can suffer nausea, cramps, bloating, gas, or diarrhea after drinking milk or eating other dairy products; but there are some who find that they can eat a few select dairy foods and others who never develop any symptoms. Population studies indicate that lactose intolerance, as this condition is called, is present in as many as 75 percent of African Americans and American Indians, and 90 percent of Asian Americans. People with lactose intolerance can take lactase tablets or drops when they eat dairy foods to aid digestion, and reduced-lactose dairy products are also available.

In addition to dairy products, other good sources of dietary calcium include canned sardines and salmon, calcium-fortified soy milk, calcium-fortified orange juice, and broccoli.

An area of striking unanimity among nutrition experts is the paramount importance of daily fruits and vegetables. They provide calories (mostly in the form of carbohydrates) along with abundant vitamins, fiber, and natural anticancer substances. A wealth of epidemiological evidence has linked high vegetable and fruit intake with a reduced risk of heart disease, stroke, diabetes, and various kinds of cancer, including cancers of the mouth and throat, lung, stomach, bladder, colon, breast, and prostate. People who regularly eat lots of fruits and vegetables have a lower frequency of constipation and gastrointestinal disorders and even gain some protection against cataracts and macular degeneration, two eye disorders common in old age.

Walter Willett of Harvard suggests in his book Eat, Drink and Be Healthy that the USDA’s “5 A Day” campaign, aimed at increasing Americans’ intake of fruits and vegetables, has somewhat misled the public by setting the bar too low. Five servings a day is the minimum recommended by national dietary guidelines, which set the serving number as a proportion of total daily calories. Children over 6, teenage girls, active women, and most men are supposed to get 7 servings a day, while teenage boys and physically active men are supposed to eat 9. For the forthcoming 2005 dietary guidelines, an advisory panel has recommended further boosting recommended daily vegetable and fruit intake. The panel advises that Americans should consume between 5 and 13 servings daily, with the recommended number for different age groups dependent on overall calorie needs.

Willett also believes that potatoes (America’s most popular “vegetable”) should not even be counted in figuring one’s daily vegetable servings because they are mostly starch and ought to belong to the bread and grain category. He suggests striving for color and variety in the diet by including offerings from several categories (dark green leafy vegetables, yellow or orange fruits and vegetables, red fruits and vegetables, beans, and citrus fruits). Fresh produce should be washed under cold running tap water before it is eaten or cooked to remove dirt, bacteria, and other residues. Vegetables with a hard surface, such as

potatoes or carrots, can be scrubbed with a brush. In a large, federally funded randomized trial, Dietary Approaches to Stop Hypertension, or DASH, researchers found that a diet containing 8 to 10 servings of fruits and vegetables per day was very effective in reducing blood pressure among people whose pressure was high enough to need medical treatment. In addition, most vegetables and fruits contain healthful fiber and have a low glycemic index: they tend to fill people up without causing rapid surges in blood sugar or insulin levels. The more of them we eat, the healthier we as a population are likely to be.

Experts, including the advisory panel for the 2005 dietary guidelines, also concur that Americans should boost their intake of whole grains and fiber. One of the best sources of fiber, whole grains also contain vitamins, minerals, and healthy unsaturated fats. Many of these valuable components are lost when grains are cracked and milled to remove their outer layers and the plant embryo portion of the seed, such as during the manufacture of white flour from whole wheat. Eating whole grains reduces the risk of diabetes, heart disease, and several kinds of cancer and prevents constipation. By switching to brown rice or whole grain pasta and by choosing breads, crackers, and cereals that list “whole wheat,” “whole oats,” “whole rye,” or another whole grain as the first ingredient on the label, families can easily incorporate more whole grains in their diets.

Fiber—also abundant in fresh fruits and vegetables and dried beans or legumes—is healthy for many reasons. It helps prevent overeating by contributing to a sense of fullness at mealtime. It keeps blood sugar from rising too fast by slowing down digestion and absorption of sugars. A high-fiber diet reduces the risk of diabetes and heart disease and prevents constipation. Some fiber remains solid (insoluble) in the digestive tract, helping make stools softer and bulkier; other fiber dissolves in intestinal fluid and traps bile acids that contain cholesterol, thereby lowering the blood level of cholesterol.

So far I have been describing what to eat as part of a healthy diet. Traditionally, that has also been the focus of the nutrition lessons children get in school. But many dietitians and educators now believe that an

important piece has been left out: teaching people how much to eat—and how to avoid overeating.

Research suggests that without realizing it Americans have shifted to consuming larger portions than they need, perhaps as a result of the “supersizing” phenomenon mentioned earlier. Parents and others who feed children can do a lot to reverse this unhealthy trend by teaching kids (and in the process themselves) how to estimate appropriate portions. The easiest starting point is to learn about standard serving sizes by reading the nutritional information on food packages or from other sources, such as the USDA Web site. The site has a helpful chart of serving sizes, along with other useful information such as the number of daily servings recommended for children of different ages. (See page 267 in Resources.) You may be surprised to discover that a “serving” of many foods is a lot smaller than you thought: for instance, 2 to 3 ounces of cooked meat or fish, 2 tablespoons of peanut butter, or 1 egg counts as a serving in the meat and beans (protein-containing) food group.

Try measuring family portion sizes at home for a few days to learn how to estimate serving sizes accurately. Figuring out how much food your cereal bowls and serving spoons actually hold will make you better at estimating. Children can help with this process and can learn how to determine the serving size by checking the nutrition labels of food packages. You can also use handy tricks. An adult’s fist or a tennis ball is about the volume of 1 cup (which is 2 servings of pasta or rice). An adult’s thumb from tip to base is about the size of 1 ounce of meat or cheese. An adult’s palm minus the fingers, or a standard-sized audiocassette, is about the size of a 3-ounce serving of cooked meat, fish, or poultry. A handful of potato chips, pretzels, or raisins is about the size of 1 serving of those foods.

Nutrition scientist Barbara Rolls has done extensive research exploring how meal composition and environmental cues unconsciously affect people’s capacity to regulate their food intake. Rolls’s findings suggest that satiation tends to occur predictably when the individual has consumed a certain weight or volume of food, not a certain number of calories. For this reason, overconsumption is much more likely when people eat foods that are high-fat and therefore “calorie dense”—that is, containing more calories per unit of weight—than when they

eat foods that are not calorie dense. Fat contains 9 calories per gram; protein and carbohydrate, 4 per gram; fiber, 1.5 to 2.5 calories per gram. Fresh vegetables and most fresh fruits have low calorie density because much of their weight is water (no calories) and fiber. Water-based soups also have a low calorie density.

Rolls’s findings form the basis for a practical, relatively low-fat approach to eating that anyone can adopt to avoid overconsuming calories. As she explains in her book Volumetrics, a key strategy is to make meals and snacks less energy dense by including lots of fresh vegetables, fruits, and fiber and by incorporating water into food (for instance, in soups, stews, and cooked grains). Much current sound nutrition advice is based on similar principles. For example, some experts recommend dividing each person’s dinner plate into imaginary sections, with two-thirds of the space devoted to vegetables, whole grains, and/or beans and one-third or less assigned to the animal protein portion. Others suggest serving salad, soup, or vegetables first (when the family is hungriest) and grain and/or protein portions afterward. Low-fat salads (made without too much dressing) help fill people up and keep them from overconsuming the more calorie dense foods on the menu. Serving vegetables and any unfamiliar or “new” foods first also makes it more likely that children will eat some of those items.

David Katz suggests using the “stoplight” concept popularized by pediatric obesity treatment expert Leonard Epstein as a tool to teach everybody better eating habits. He feels it could even be used on food labels. In this scheme, foods in the “green” category, such as vegetables, fruits, and some whole grains that are low in energy density and high in nutrients, can be eaten in large quantities. Most foods are “yellow,” with moderate energy density and nutrient content; they should be eaten regularly in moderation. “Red” foods, such as desserts, are high in calories and low in nutrients and should be eaten as treats, in small quantities. It’s a good idea to keep plenty of “green” foods visible in the kitchen and refrigerator for kids to grab when they’re looking for a snack.

At David Ludwig’s OWL clinic in Boston, the eating plan that was taught to Adam and his family uses a somewhat different approach based on foods’ glycemic index—but there too the goal is to help chil-

dren achieve and maintain a healthy weight by avoiding overconsumption of calories. Like Rolls’s volumetrics strategy, it’s meant to be a long-term approach to eating, not a temporary measure. The concept of foods’ glycemic index originated as a way of studying how various foods affected the ups and downs of blood sugar in people with diabetes. Researchers reasoned that since some foods raise blood glucose levels faster and higher than others, designing a diabetic person’s diet to include foods with a low glycemic index might be useful as part of treatment. Such a diet might cause smaller swings in blood glucose levels and thereby allow diabetics to reduce the dose of injected insulin. One of the earliest studies on the concept, published in 1983 in the New England Journal of Medicine, contained the surprising finding that eating a potato raised blood glucose levels as rapidly as eating a comparable amount of carbohydrate in the form of sugar. Since the 1980s about a dozen studies have indeed found that low-glycemic-index diets improve blood sugar control in diabetes. Although such diets are not yet routinely recommended by the American Diabetes Association, which cites the need for additional research, the approach has been endorsed by diabetes associations in several other countries.

Even in nondiabetics, there is reason to suspect that the big boost in blood glucose caused by meals full of high-glycemic-index carbohydrates may not be healthy. Such foods (potatoes, white bread, sweets, bagels, and many other baked goods, for example) send blood glucose level rapidly upward, triggering abundant release of insulin. Insulin’s message to the body is, store these calories immediately! In response, glucose is quickly taken up by muscle cells and by the liver (which conserves it as a starch called glycogen), while free fatty acids in the bloodstream are quickly sopped up by fat cells. Within a few hours the body’s efficient storage action makes blood glucose drop steeply. Since the brain needs a constant supply of glucose to function, the sudden drop sets off alarm signals, instructing the system to switch gears from storing energy to making it available. Another set of hormones—epinephrine, glucagons, cortisol, and growth hormone—brings the blood’s glucose level back up to within a more normal level. Ludwig’s research suggests that one of the actions of these hormones is to trigger intense hunger for the next meal.

In one study Ludwig and several colleagues divided 12 obese teenage boys into three groups and fed each group a different test meal. Two of the meals were identical in total calories and in the proportion of calories that came from each category of nutrient, but one had a medium glycemic index (for instance, it contained steel-cut oatmeal) and one had a high glycemic index (it contained instant oatmeal). The third test meal had exactly the same number of calories as the other two but contained foods with a low glycemic index: a vegetable omelet and fresh fruit. Everyone in a group received that group’s test meal for both breakfast and lunch. The participants’ levels of glucose, fatty acids, insulin, and other hormones were measured at intervals after the meals. The boys were asked to rate their hunger level at various times throughout the day. During the five-hour period after lunch, food was freely available and the participants’ requests for food and food intake were recorded.

The high-glycemic-index meal provoked a much bigger and more sustained rise in glucose than the low-glycemic-index meal and a correspondingly greater surge in insulin. By five hours after breakfast the blood glucose levels of boys who had eaten the high-glycemic-index meal had plummeted to below their original fasting levels, while the glucose levels in boys who ate the low-glycemic-index meal had come down only gradually, reaching about the original fasting level. Throughout the day, boys who ate the high-glycemic-index meal reported greater hunger than those in the other two groups. By the end of the day (after snacking in the afternoon on food that was freely available to all groups), the boys given the high-glycemic-index meal had eaten 81 percent more total calories than the boys given the low-glycemic-index meal. Those given the medium-glycemic-index meal had eaten 53 percent more calories than the low-glycemic-index group. The implication of these findings is that eating lots of carbohydrates with a high glycemic index may put the body on a metabolic and hormonal seesaw whose net result is increased hunger and higher total calorie consumption. A calorie is still a calorie—and eating excess calories will cause weight gain, regardless of whether those calories come from carbohydrates, proteins, or fats, but the overall makeup of the diet might indirectly influence how many calories are ingested.

When the government began urging Americans to reduce their to-

tal fat intake, Ludwig notes, “the food industry came in and encouraged us to be eating low-fat foods that were high in starch and sugar, instead of [promoting] fruits and vegetables. You can’t brand broccoli as easily as you can muffins. When fat got replaced by starch and sugar rather than by fruits and vegetables, the bargain may have been a bad one for body weight regulation.”

Ludwig’s research on how the body adapts to a calorie-restricted diet aimed at producing weight loss suggests that a low-glycemic-index diet might be less likely than a high-glycemic-index diet to trigger counterproductive physiological defenses against weight loss. For instance, in a recent 12-month study, 16 overweight teenagers were randomly assigned either to a calorie-restricted low-fat diet (25 to 30 percent fat, 55 to 60 percent carbohydrate) or to a low-to-moderate-glycemic-index diet (30 to 35 percent fat, 45 to 50 percent carbohydrate). Those in the low-glycemic-index group were counseled to include some protein and fat along with their carbohydrates at every meal and snack, but unlike the low-fat group, their calories were not restricted: they were told to eat until they were satisfied and to snack when hungry. Both groups received identical behavioral therapy and physical activity recommendations, and both followed their diets for six months. Then they were monitored for another six months. Seven participants in each group completed the study. At the end of one year, those in the low-glycemic-index group (despite the lack of calorie restriction) had lost significantly more weight and more fat—11 pounds more on average—than those in the low-fat group.

In the competition among nutrition researchers over how to build a better food pyramid, David Ludwig and his colleague Cara B. Ebbeling have their own entry. It reflects a diet based on foods with a low glycemic load (a term that reflects both a food’s glycemic index and its total carbohydrate content). Unlike the USDA Food Guide Pyramid, it makes fruits and vegetables the foundation. Grain-based foods have been moved farther up the pyramid and thus make up a smaller proportion of the diet than in the USDA version. Protein (in the form of nuts, dairy, poultry, and fish) is featured a bit more prominently.

No large long-term studies of low-glycemic-index diets have yet

been conducted. Some experts are wary of advising consumers to use the glycemic index as a tool for choosing what to eat. They note that any food’s impact on the blood glucose level depends not only on its glycemic index but on the quantity consumed and on whether it is eaten along with other foods that might slow the absorption of nutrients from the intestinal tract. Nutrition researcher William Dietz says he is not convinced that foods’ low glycemic index accounts for the weight loss seen among participants in Ludwig’s studies. “I think the diets induce weight loss, but I question whether it’s the glycemic index or the high water content of the fruits and vegetables in the diet,” Dietz says.

Parents and other consumers can leave the wrangling over details to the nutrition scientists. There is practical wisdom to be extracted from the research of Rolls, Ludwig, Willett, and others—and their take-home messages are not really so far apart. Boiled down to essentials, the kinds of foods recommended for a low-glycemic-index diet are not especially radical; in fact, they fit easily within the framework of the general noncontroversial dietary advice detailed earlier in this chapter. As Ludwig summarized his basic instructions in a recent medical article, “Increase consumption of fruits, vegetables and legumes (beans), choose grain products processed according to traditional rather than modern methods (pasta, stone-ground breads, old-fashioned oatmeal, for example), and limit intake of potatoes and concentrated sugar.”

There’s plenty of common ground among nutrition experts, and consumers can’t go wrong by basing their diet on the areas of consensus. Eat lots of fresh vegetables and fruits, whole grains, and fiber. Choose fat-free or low-fat dairy products. Maintain a moderate protein intake. Substitute “healthy” fats for unhealthy ones. Limit total fat intake. Cut back on foods and drinks that are high in added sugars, fat, or highly processed carbohydrates. These are the lessons the science teaches. It’s not so hard for a family to apply them and adopt a healthy way of eating. As Adam says, “It’s one of the easiest things I do.”

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