Forget the scale, the calorie counting, and forbidden foods. They may be doing more harm than good
It's diet season, that time of year when more than 76 million Americans resolve to never eat another french fry, swear off sweets, stop swilling beer, and pray for a magic pill to shorten the days of diet deprivation that so often mark the new year. The call is everywhere. Good Morning America is featuring weight-loss tips every day this month. AOL tells its subscribers via E-mail that it's "Time to lose your spare tire."NBC last week rolled out a special edition of its obesity reality show, The Biggest Loser. Magazines lining grocery aisles exhort you to "Lose 10 pounds this month!"
But can you lose 10 pounds in a month and keep it off? Americans spend more than $33 billion a year on diet books, foods, programs, gadgets, and DVDs in the hopes of losing weight. Yet, after decades of dieting, about two thirds of the American population remains overweight. Some 30 percent are obese, and more than half of them are dieting. Which raises the question: Does dieting work? Do people lose weight permanently on diets? Does dieting lead to better health?
Nutritionists, exercise physiologists, and other health professionals are asking these questions with increasing frequency. And a small but growing number of them believe that the solution is simple: Stop dieting. Stop obsessing about every morsel you put in your mouth, stop weighing yourself twice a day, stop letting the quest to be thin control your life. "I'm almost convinced that dieting is totally useless," says Cris Slentz, an exercise physiologist at Duke University Medical Center. "It's the physical activity aspect of our lifestyle that is the main culprit in our overweight problems. Most of us are eating 25 to 100 calories a day too many, and gaining 10 pounds or less per year. Our appetite system really works pretty well. So why would we use a 1,000 calorie per day deficit diet to try to correct the weight imbalance? It's nuts, and it isn't leading to long-term healthy weights." Steven Hawks, a professor of health science at Brigham Young University, agrees. "You would be hard pressed to review the dietary literature," he says, "and conclude that you can give people a set of dietary guidelines or restrictions that they will be able to follow in the long term and manage their weight successfully."
Slentz, Hawks, and other researchers note that most studies show that the vast majority of people can't stick with a diet very long. Though some dieters do make lifestyle changes that lead to permanent weight loss and better health, most regain much, if not all, of their lost weight in three to five years. Results reported last week from the federally funded Women's Health Initiative do little to enhance dieting's reputation. After seven years, women on a low-fat diet maintained a mere pound of their initial loss. And some studies show that frequent dieters actually gain weight.
Yet, dieting to achieve weight loss has been a cornerstone of obesity treatment, because excess weight is associated with high blood pressure, unhealthy cholesterol levels, metabolic syndrome, and other cardiovascular risks and increases the likelihood of developing type 2 diabetes and some cancers. But stop-dieting advocates point out that many other factors also contribute to these conditions: age, family history, gender, diet quality, stress, socioeconomic status, vitamins, and minerals--and some of these causes are more significant than weight.
While losing modest amounts of weight often lessens the impact of such health problems, so do regular exercise and healthful eating. "Even in heart disease, the role of fat tissue itself is small compared to the role of diet and exercise," says Linda Bacon, a nutrition professor at the University of California-Davis. "Since diet and exercise is the stuff that really matters, let's go after it directly and not use weight loss as the goal."
Fitness counts. Obesity, defined as a body mass index (a measure of height versus weight) over 30, does seem to increase mortality, but a study published last year in the Journal of the American Medical Association by the Centers for Disease Control and Prevention showed that increased deaths linked to obesity occur largely among those with BMIs over 35--people who carry an extra 50 or more pounds. The study revealed that Americans who are merely overweight--with BMIs between 25 and 30--actually live longer than people of normal weight. This may be due in part, the authors suggest, because new drugs to treat hypertension and cholesterol have reduced the negative impact of weight.
For years, research by Steven Blair, CEO of the Cooper Institute in Dallas, has shown that men and women who achieve a high level of fitness, regardless of weight, live longer and develop fewer chronic illnesses than thin people who aren't fit. It's also not clear that weight loss can make a heavy person's body the same as the body of a person who is naturally thin. Research on the role fat cells play and the impact of genes on weight gain, in fact, indicate that overweight bodies are never the same as naturally thin ones--no matter how much weight people lose.
Nevertheless, diets sell books, attract media attention, and fatten the wallets of authors who write them far more than they slim the bodies of the people who try them. Most popular diets seem to produce about the same modest weight loss. A study last year in JAMA looked at four such diets: Atkins (low carb), Ornish (low fat), Weight Watchers (low calorie), and the Zone (low glycemic load). Participants were randomly assigned to each diet. Only 50 to 65 percent of dieters stuck with the plans long enough to lose weight. But the ones who did lost between 4.6 and 7.3 pounds in a year and improved some of their cardiac risk factors, such as cholesterol levels. Michael Dansinger, an endocrinologist at the Tufts-New England Medical Center and lead researcher of the trial, calls the results "underwhelming."For her part, Karen Miller Kovach, chief scientific adviser for Weight Watchers, says "Weight Watchers has never preached diet alone as a means to lasting weight loss. But diet is part of the comprehensive lifestyle program."
Many experts were anxiously awaiting the first chapter in the Women's Health Initiative dietary modification study, probably the largest trial of a low-fat diet ever done, which was reported last week in the same journal. It showed that among more than 19,000 post-menopausal women, a low-fat, high-carbohydrate diet does not cause weight gain, as some low-carb enthusiasts have claimed. But it resulted in little long-term weight loss, either. Women in the study lost about 5 pounds the first year and kept off only about 1 pound over the seven years of the study.
Weight loss was not the point of the study; the WHI is evaluating the effect of a low-fat diet on breast and colorectal cancer. "But a major dietary intervention study like this with such modest weight change underscores the dismal track record of failure to find dietary interventions that promote long-term weight loss," says Dansinger. Barbara Howard, president of the MedStar Research Institute, who led the WHI study, sees it differently. She was encouraged that some women increased their servings of fruit and vegetables to five a day, and notes that those were the women who lost the most weight. "It's hard for people to make changes," says Howard. "We need to be realistic in terms of what dietary modifications are possible."
Biology seems to work against long-term weight loss. Michael Rosenbaum, an associate professor of clinical medicine at the Columbia College of Physicians and Surgeons, believed leptin, a hormone secreted by fat cells, might be the culprit causing weight regain after dieting. "When your leptin level is low for you--and it's different for everybody--your body reacts by lowering your energy expenditure, increasing the efficiency of your muscles, and favoring restoration of leptin levels to their usual values," says Rosenbaum. That seems to trigger the weight return.
And there is no evidence that a previously fat body ever becomes accustomed to the drop in leptin. Rosenbaum points to the successful losers in the ongoing National Weight Control Registry, some 5,000 people who have lost 30 pounds or more and maintained the loss for at least a year. Registry participants used every imaginable diet. But maintaining their losses is a major effort. Most eat a low-calorie, low-fat diet, record food intake, and exercise an hour a day or more to override their bodies'biological drive to regain. "A person who maintains even a small degree of weight loss has done an amazing thing," Rosenbaum says. "Evolution favors fatness."
Diet yo-yo. That may be why some research indicates that frequent dieting leads to weight gain. In a 2004 study in the Journal of the American Dietetic Association of 149 obese women, those who had dieted before age 14 were more than twice as likely to have dieted 20 times or more and had the highest BMIs. The vast majority of the women, 79 percent, had not been able to maintain any permanent weight loss, though 9 percent kept off a loss of 20 pounds or more. Joanne Ikeda, a nutrition specialist at the University of California-Berkeley and the lead author of the study, says that these women had become very vulnerable to yo-yo dieting, which often leads to higher permanent weights. "There is a subset of people," says Ikeda, "and we can't identify those people yet, but their bodies become more and more efficient at fat storage and they become less able to take weight off."
Still, neither biology nor yo-yo dieting tells the whole story. Genes also play a role. Older studies of twins estimated that as much as 70 percent of adult body weight is inherited. In a 2004 study, James Romeis, a professor of health services research at St. Louis University, looked at the weight of Vietnam War-era twins who were at normal weight when they entered the military and gained as they grew older. "You end up with about 50 percent of weight gain or weight change being genetically influenced," Romeis says. "So, if you were born with the genes that contribute to weight gain, then you've got to work doubly hard to take it off."
Despite the impact of biology and genetics, about half of all weight gain is due to our environment and our increasingly sedentary lifestyle. So the real question may not be, What's the best diet? but: What can I do to manage my weight and improve my health? "The goal of weight loss is supposed to be good health," says Columbia's Rosenbaum, "not some cosmetic standard of beauty. So our focus needs to be on health, not weight." Some nutritional scientists are looking at ways to move Americans toward these healthier alternatives, and some are responding.
Carol Holt, 43, a nurse and management consultant in Tustin, Calif., had given up on diets after she lost 100 pounds--twice--but started to regain. At that point, Holt sought the help of Evelyn Tribole, a registered dietitian and the author of Intuitive Eating, a guide to eating based on biological cues of hunger and satiety. Holt has thus far maintained about 60 pounds of her second 100-pound loss. Supersize portions have made many forget what a comfortable level of fullness feels like, says Tribole, and one has to abandon diets, rules about food, eating while multitasking, and anything else that interferes with recognizing fullness, taste, and satisfaction. If a food doesn't taste good or meet expectations, she says, don't eat it. Figuring out how to eat intuitively takes time, Tribole adds, as should meals. "Savor your eating."
BYU's Hawks switched to intuitive eating several years ago after a lifetime of failed diets. In the past year or so, he has lost 50 pounds. "Learning to recognize biological hunger and respond to it in the most satisfying way," he says, "is the best hope for managing weight long term."
One step. Many scientists believe that breaking each change down into a series of small steps is less overwhelming than a complete lifestyle overhaul. You might decide, for example, to begin eating a large apple every day for an afternoon snack instead of a bag of chips or cookies. An apple is filling; it's lower in calories, higher in fiber, packs many more nutrients, and adds another serving of fruit. Within a week, it's a new habit. Next, you might start dinner with a salad, easy on the dressing. Salad is low in calories and adds fiber and nutrients, and studies show eating a salad before dinner reduces the amount of total calories in the meal by 7 to 12 percent.
One proponent of the small-steps approach is Barbara Rolls, professor and Gutherie chair in nutrition at Pennsylvania State University and author of The Volumetrics Eating Plan, a guide to preparing satisfying meals that are lower in calories. Rolls was among the first to realize that humans eat about the same weight or volume of food every day. So if they can prepare dishes that make them feel satisfied with fewer calories, it's easier to manage weight. The key to satiety with few calories, says Rolls, is to eat foods that are less energy dense, rich in water and nutrients but not high in calories--foods like fruits, vegetables, soups, stews, and salads. Her studies show that when overweight people eat this way, over time they lose weight.
The Health at Every Size movement was initially a response to futile dieting, as well as a reaction to societal discrimination against those who are overweight. Its basic principles: healthful changes in food selection and physical activity but no prescriptive dieting or calorie counting. Like Intuitive Eating, HAES advocates believe people should be guided by fullness cues.
HAES principles formed the basis of a U.S. Department of Agriculture-funded program in Wyoming, Idaho, and Montana, in communities where 70 percent of men and 59 percent of women were overweight. From 2001 through 2003, Wellness in the Rockies offered nutrition lessons, trained participants in listening to hunger and fullness cues, provided pedometers, and offered discount coupons on fruits and vegetables. Weight and average BMI of the participants changed very little. "But when you realize that most people are gaining a pound or more every year," says Michael Liebman, professor of nutrition at the University of Wyoming and a project leader, "even maintaining is a positive step forward."
Not everyone agrees. "You hate to have people giving up on weight loss as a possibility," says Kelly Brownell, director of the Yale Center for Eating and Weight Disorders. "On the other hand, the whole idea of body acceptance and eating for the sake of health has positive aspects." But that doesn't attract headlines. Still, "the bottom line is learning to make subtle, lifestyle changes that can be maintained indefinitely," says Liebman. "It's not glitzy."
This story appears in the January 16, 2006 print edition of U.S. News & World Report.