Doctors aren’t supposed to write prescriptions for medications they know don’t work. So why do they and many leading public health authorities continue to dispense advice that may be no more effective than a sugar pill—and might actually cause harm? In a landmark review published earlier this year in Nutrition Journal, the authors question why doctors and other medical experts routinely counsel over-weight people to get rid of extra pounds even though scientists, after decades of intense research, have yet to find a reliable prescription for weight loss. Moreover, the payoff for dieting isn’t even clear: There’s little evidence that losing weight is the key to better health, contends lead author Linda Bacon, PhD, a nutrition professor at the City College of San Francisco. And in some cases, she adds, efforts to shed pounds may actually be dangerous.
In her well-informed critique, Bacon not only raises questions about conventional weight-loss notions but also posits that there are more effective paths to better health. More asked her for details.
What’s wrong with dieting—that is, restricting your food intake to lose weight?
A The first thing that’s wrong is that dieting almost never works. A few years ago, psychologist Traci Mann, PhD, and her colleagues at the University of California, Los Angeles, reviewed two decades of studies of weight-loss programs. They found that dieters initially dropped pounds, usually 5 to 10 percent of their body weight. But when these dieters were followed over time, they almost all regained the weight they’d lost. In general, the more time that passes after someone loses weight on a diet, the more weight she regains, until she’s back to where she was or is even heavier. Results like these led a panel of experts convened by the National Institutes of Health to acknowledge that no matter what weight-loss plan people follow, almost all of them regain weight. There’s no evidence that diets lead to lasting weight loss.
But aren’t there some successful losers out there? Hasn’t the National Weight Control Registry [NWCR] been keeping a list of them in order to figure out what works?
A Of course there are successes. But very, very few. The NWCR tracks people who have lost 30 pounds or more, but for as little as one year. Also, the number of people in the registry is a tiny portion of the total group of Americans trying to lose weight. In general, the scientific and popular literature estimates that only about 5 percent of dieters maintain their weight loss, which is dismal. To insist that everyone do what only a small fraction of people have succeeded at is to set up the majority for failure. It’s not that dieters fail. It’s the concept of dieting that fails.
Still, Americans have grown fatter over the past 30 years. Don’t we need to stem the rising epidemic of obesity?
A The term epidemic is misleading. It’s true that average weight has increased. But the word epidemic implies a public health crisis. There’s no evidence that Americans’ being heavier, on average, poses a serious health threat.
Then why are there these warnings about the dangers of excess weight? Last year researchers from the Centers for Disease Control and Prevention reported that people who are obese at age 45 are less likely to survive to age 65 than people at a healthy weight. A Harvard study, also published last year, showed that the risk of heart disease was more than twice as high among people with a body mass index over 30. Shouldn’t those findings alarm us?
A Studies like these find associations, not cause and effect. Unfortunately, there’s been a widespread rush to conclude that being fat causes illness. Neither of the studies you mentioned took physical activity into account, for example, yet it’s much more likely that being sedentary, not being fat, is the real problem. When researchers have looked at physical activity, the association between health and BMI gets much smaller. A 2008 study, done by Harvard researchers, looked into the effects of physical activity and body mass index on coronary heart disease and found that overweight women who walked more than four hours a week had a significantly lower risk of heart disease than those who didn’t exercise. This says to me that the most important risk factor isn’t being fat; it’s being sedentary.
What about type 2 diabetes? Its incidence is rising, and experts link it to excess weight.
A It is true that type 2 diabetes is more common in people who are heavier. However, researchers have been too quick to assume that being fat is the primary cause of insulin resistance, which in turn leads to type 2 diabetes. We know that insulin resistance causes people to gain weight. The bigger part of the story may be that weight gain is a consequence of insulin resistance rather than the other way around. Insulin resistance is related to many factors, such as genetics, what people eat and how much exercise they get. We’d be much more effective at addressing diabetes if we paid more attention to behavioral factors than to body size. There are millions of people who are defined as obese but are very healthy. One important study, an analysis of more than 5,000 participants in a national government sample, showed that 35 percent of obese women don’t have the constellation of health problems typically linked to higher weight. Specifically, they showed no more than one sign of these issues: high blood pressure, high triglycerides, low HDL [“good”] cholesterol, elevated glucose levels, insulin resistance and systemic inflammation. And there are some health concerns, such as osteoporosis, that are much less common in people categorized as overweight or obese.
Are you suggesting that being overweight or obese may actually be an advantage?
A There’s something researchers call the “obesity paradox”—that people who are heavier tend to survive longer than thinner people with the same disease. In one early study, researchers looked at patients with heart failure, assuming that obese people would fare worse than thin people. The opposite turned out to be true. Obese patients who suffered heart failure survived longer than nonobese people with the same history. If you look at people diagnosed with cardiovascular disease in general, those who are categorized as obese have greater longevity than people who are thin. The same holds true for chronic kidney disease, hypertension and even type 2 diabetes. Why isn’t entirely clear. But the findings call into question the widely held belief that being overweight or obese is always dangerous and suggest that it may be protective in some ways.
You’ve made the point that dieting for weight loss rarely works. You’ve also warned that these diets can be hazardous to one’s health. What’s dangerous about losing weight?
A Dropping pounds through dieting has been shown to cause some health problems, including reduced bone mass, which increases the risk for osteoporosis. But the biggest problems probably result from weight cycling, or yo-yo dieting, which is the reality for most people who try to lose weight. Weight cycling has been linked to a host of concerns, including raised cholesterol levels, higher blood pressure, increased inflammation, insulin resistance and even depressed immune function. Consider high blood pressure, which is often associated with obesity. When researchers at the German Institute of Human Nutrition in Potsdam-Rehbrücke looked at more than 12,000 middle-aged men and women for a study published in 2005, they found that obese men and women whose weight fluctuated over a two-year period were four times as likely to develop hypertension as the obese people whose weight remained stable. An earlier Italian study reported that women who had lost weight at least five times in five years were more likely to have high blood pressure than those whose weight remained stable.
If dieting is a bad idea, what should the public health message be?
A Our focus on weight has resulted in widespread body discontent rather than improved health in the popula-tion. Instead, we should be focusing our efforts on what people can do and what we know will make them healthier—such as being physically active and eating more nutritious foods. My colleagues and I did a study, reported in the Journal of the American Dietetic Association, that confirms the usefulness of this approach. We randomly divided 78 obese chronic dieters, all female, into two groups: One followed a conventional weight-loss diet; the other enrolled in the Health at Every Size [HAES] plan, which emphasizes eating in response to hunger cues. Both programs lasted six months, and subjects were evaluated two years after the study’s beginning. By six months, 42 percent of the conventional-diet-program participants had dropped out, but only 8 percent of the HAES members had departed. The dieters did lose weight in the first six months, but two years later they had, on average, regained it all. Women in the HAES group did not lose or gain weight; they stayed the same weight throughout the two years. By the end of the study period, the HAES women showed significant improvements in their LDL [“bad”] cholesterol and systolic [the top number] blood pressure; the dieting group ended up where it had started. In addition, 53 percent of those following a diet reported feeling like failures; none of the HAES women did. So I think our message needs to encourage people to become healthy rather than focus on weight loss.
Let’s face it, though: A lot of people want to lose weight because they don’t like the way they look. What’s your advice to them?
A We need to resist the notion that being thin is the path to happiness. It isn’t. Trying to become thin can make people very unhappy. We’ve become so obsessed with weight that it’s a major revolution for people to say, “Hey, I can choose to see myself as attractive.” We’d all be much happier if we honored size diversity and focused on healthy choices, letting our weight fall naturally where it may.
[THE IMPACT OF OTHERS]
Mirror, mirror, on the wall, who has the best body image of all? When Tracy Tylka, PhD, associate professor of psychology at Ohio State University in Columbus, polled 801 women about body image for a study published in January, their responses surprised her. “We assumed that the biggest factor would be how much a woman weighs, given the emphasis on weight in our culture,” says Tylka. Instead, her findings showed that the most powerful influence was the opinion of others. “If a woman is surrounded by people who accept her as she is, who don’t talk about weight in a negative way, she’s much more likely to have a positive body image,” she explains. “No matter how heavy a woman was, if she had positive social support, she tended to have a positive body image.”
Liking your reflection in the mirror is more than a matter of vanity. A positive body image is associated with life satisfaction, better coping skills and healthy behaviors, including more physical activity and good eating habits. “Women who appreciate their bodies are more likely to take care of themselves—for example, by getting regular breast-cancer screenings,” says Tylka.
Originally published in the October 2011 issue of More.
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