Diets do not work: The thin evidence that losing weight makes you healthier.

Planning to Go on a Diet? One Word of Advice: Don’t.

Planning to Go on a Diet? One Word of Advice: Don’t.

Health and medicine explained.
March 24 2015 3:00 AM

The Weight of the Evidence

It’s time to stop telling fat people to become thin. 

Illustration by Robert Neubecker.

Illustration by Robert Neubecker

If you’re one of the 45 million Americans who plan to go on a diet this year, I’ve got one word of advice for you: Don’t.

You’ll likely lose weight in the short term, but your chance of keeping if off for five years or more is about the same as your chance of surviving metastatic lung cancer: 5 percent. And when you do gain back the weight, everyone will blame you. Including you.

This isn’t breaking news; doctors know the holy trinity of obesity treatments—diet, exercise, and medication—don’t work. They know yo-yo dieting is linked to heart disease, insulin resistance, higher blood pressure, inflammation, and, ironically, long-term weight gain. Still, they push the same ineffective treatments, insisting they’ll make you not just thinner but healthier.

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In reality, 97 percent of dieters regain everything they lost and then some within three years. Obesity research fails to reflect this truth because it rarely follows people for more than 18 months. This makes most weight-loss studies disingenuous at best and downright deceptive at worst.

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One of the principles driving the $61 billion weight-loss industries is the notion that fat is inherently unhealthy and that it’s better, health-wise, to be thin, no matter what you have to do to get there. But a growing body of research is beginning to question this paradigm. Does obesity cause ill health, result from it, both, or neither? Does weight loss lead to a longer, healthier life for most people?

Studies from the Centers for Disease Control and Prevention repeatedly find the lowest mortality rates among people whose body mass index puts them in the “overweight” and “mildly obese” categories. And recent research suggests that losing weight doesn’t actually improve health biomarkers such as blood pressure, fasting glucose, or triglyceride levels for most people.

So why, then, are we so deeply invested in treatments that not only fail to do what they’re supposed to—make people thinner and healthier—but often actively makes people fatter, sicker, and more miserable?

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Weight inched its way into the American consciousness around the turn of the 20th century. “I would sooner die than be fat,” declared Amelia Summerville, author of the 1916 volume Why Be Fat? Rules for Weight-Reduction and the Preservation of Youth and Health. (She also wrote, with a giddy glee that likely derived from malnutrition, “I possibly eat more lettuce and pineapple than any other woman on earth!”) As scales became more accurate and affordable, doctors began routinely recording patients’ height and weight at every visit.  Weight-loss drugs hit the mainstream in the 1920s, when doctors started prescribing thyroid medications to healthy people to make them slimmer. In the 1930s, 2,4-dinitrophenol came along, sold as DNP, followed by amphetamines, diuretics, laxatives, and diet pills like fen-phen, all of which caused side effects ranging from the annoying to the fatal.

The national obsession with weight got a boost in 1942, when the Metropolitan Life Insurance Company crunched age, weight, and mortality numbers from policy holders to create “desirable” height and weight charts. For the first time, people (and their doctors) could compare themselves to a standardized notion of what they “should” weigh. And compare they did, in language that shifted from words like chubby and plump to the more clinical-sounding adipose, overweight, and obese. The word overweight, for example, suggests you’re over the “right” weight. The word obese, from the Latin obesus, or “having eaten until fat,” conveys both a clinical and a moral judgment.

In 1949, a small group of doctors created the National Obesity Society, the first of many professional associations meant to take obesity treatment from the margins to the mainstream. They believed that “any level of thinness was healthier than being fat, and the thinner a person was, the healthier she or he was,” writes Nita Mary McKinley, a psychologist at the University of Washington-Tacoma. This attitude inspired a number of new and terrible treatments for obesity, including jaw wiring and stereotactic brain surgery that burned lesions into the hypothalamus.

Bariatric surgery is the latest of these. In 2000, about 37,000 bariatric surgeries were performed in the United States; by 2013, the number had risen to 220,000. The best estimates suggest that about half of those who have surgery regain some or all of the weight they lose. While such surgeries are safer now than they were 10 years ago, they still lead to complications for many, including long-term malnutrition, intestinal blockages, disordered eating, and death. “Bariatric surgery is barbaric, but it’s the best we have,” says David B. Allison, a biostatistician at the University of Alabama-Birmingham.

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Reading the research on obesity treatments sometimes feels like getting stuck in an M.C. Escher illustration, where walls turn into ceilings and water flows upward. You can find studies that “prove” the merit of high-fat/low-carb diets and low-fat/high-carb diets, and either 30 minutes of daily aerobic exercise or 90 minutes. You’ll read that fen-phen is safe (even though the drug damaged heart valves in a third of those who took it). Studies say that orlistat (which causes liver damage and “uncontrollable” bowel movements) and sibutramine (which ups the risk of heart attacks and strokes) are effective. After reading literally more than a thousand studies, each of them claiming some nucleus of truth, the only thing I know for sure is that we really don’t know weight and health at all.

“We make all these recommendations, with all this apparent scientific precision, but when it comes down to it we don’t know, say, how much fat someone should have in their diet,” says Asheley Skinner, a pediatrician at the University of North Carolina–Chapel Hill School of Medicine. “We argue like we know what we’re talking about, but we don’t.”

Photo illustration by Slate. Photo by Thinkstock

For instance, much of the research assumes that when fat people lose weight, they become “healthy” in the same ways as a thinner person is healthy. The evidence says otherwise. “Even if someone loses weight, they will always need fewer calories and need to exercise more,” says Skinner. “So we’re putting people through something we know will probably not be successful anyway. Who knows what we’re doing to their metabolisms.”

Debra Sapp-Yarwood, a fiftysomething from Kansas City, Missouri, who’s studying to be a hospital chaplain, is one of the three percenters, the select few who have lost a chunk of weight and kept it off. She dropped 55 pounds 11 years ago, and maintains her new weight with a diet and exercise routine most people would find unsustainable: She eats 1,800 calories a day—no more than 200 in carbs—and has learned to put up with what she describes as “intrusive thoughts and food preoccupations.” She used to run for an hour a day, but after foot surgery she switched to her current routine: a 50-minute exercise video performed at twice the speed of the instructor, while wearing ankle weights and a weighted vest that add between 25 or 30 pounds to her small frame.

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“Maintaining weight loss is not a lifestyle,” she says. “It’s a job.” It’s a job that requires not just time, self-discipline, and energy—it also takes up a lot of mental real estate. People who maintain weight loss over the long term typically make it their top priority in life. Which is not always possible. Or desirable.

While concerns over appearance motivate a lot of would-be dieters, concerns about health fuel the national conversation about the “obesity epidemic.” So how bad is it, health-wise, to be overweight or obese? The answer depends in part on what you mean by “health.” Right now, we know obesity is linked with certain diseases, most strongly type 2 diabetes, but as scientists are fond of saying, correlation does not equal causation. Maybe weight gain is an early symptom of type 2 diabetes. Maybe some underlying mechanism causes both weight gain and diabetes. Maybe weight gain causes diabetes in some people but not others. People who lose weight often see their blood sugar improve, but that’s likely an effect of calorie reduction rather than weight loss. Type 2 diabetics who have bariatric surgery go into complete remission after only seven days, long before they lose much weight, because they’re eating only a few hundred calories a day.

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Disease is also attributed to what we eat (or don’t), and here, too, the connections are often assumed to relate to weight. For instance, eating fast food once a week has been linked to high blood pressure, especially for teens. And eating fruits and vegetables every day is associated with lower risk of heart disease. But it’s a mistake to simply assume weight is the mechanism linking food and disease. We have yet to fully untangle the relationship.

Higher BMIs have been linked to a higher risk of developing type 2 diabetes, heart disease, and certain cancers, especially esophageal, pancreatic, and breast cancers. But weight loss is not necessarily linked to lower levels of disease. The only study to follow subjects for more than five years, the 2013 Look AHEAD study, found that people with type 2 diabetes who lost weight had just as many heart attacks, strokes, and deaths as those who didn’t.

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Not only that, since 2002, study after study has turned up what researchers call the “obesity paradox”: Obese patients with heart disease, heart failure, diabetes, kidney disease, pneumonia, and many other chronic diseases fare better and live longer than those of normal weight.

Likewise, we don’t fully understand the relationship between weight and overall mortality. Many of us assume it’s a linear relationship, meaning the higher your BMI, the higher your risk of early death. But Katherine Flegal, an epidemiologist with the CDC, has consistently found a J-shaped curve, with the highest death rates among those at either end of the BMI spectrum and the lowest rates in the “overweight” and “mildly obese” categories.

None of this stops doctors and researchers from recommending weight loss for health reasons. Donna Ryan, professor emeritus at the Pennington Biomedical Research Center in Baton Rouge, co-chaired the National Institutes of Health panel that recently developed new guidelines for treating obesity, including calorie-restricted diets and commercial diet programs. “Those who have a BMI of 30 and up need treatment, no questions asked,” they wrote. I asked Ryan why, given that so few people keep weight off and given the risks of yo-yo dieting, the committee backed the same old ineffective treatments. “I’m not familiar with any of the research that says yo-yoing is bad for you,” Ryan told me. “I’m not convinced there’s any harm whatsoever in losing and regaining weight.”

Why do doctors keep prescribing treatments that don’t work for a condition that’s often benign? I suspect one reason lies in the fanaticism that often seems to drive the public debate around weight. Last January, for instance, when Flegal’s meta-analysis showing a low risk of death for overweight people hit the news, one of its most vocal critics was Walter Willett, an epidemiologist at the Harvard School of Public Health. He told a reporter from NPR, “This study is really a pile of rubbish, and no one should waste their time reading it.” A month later, Willett organized a symposium at Harvard just to attack Flegal’s findings.

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Willett’s career, like countless others’, has been built on the obesity-will-kill-you paradigm. Tam Fry, a spokesperson for the National Obesity Forum in the U.K., also dissed Flegal’s work. “This is a horrific message to put out,” he told the BBC. “We shouldn’t take it for granted that we can cancel the gym, that we can eat ourselves to death with black forest gateaux.”

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Actually, Flegal’s findings suggest nothing of the kind. But Willett, Fry, and others seem to see them as a dangerous challenge to a fundamental truth. UCLA sociologist Abigail Saguy, author of What’s Wrong With Fat?, says people are often invested in their own thin privilege. “They want to think they’ve earned it by working hard and counting calories, and they cling to it,” she says.

There’s a lot of money at stake in treating obesity. The American Medical Association—against the recommendations of its own Committee on Science and Public Health—recently classified obesity as a disease, and doctors hope insurers will start covering more treatments for obesity. If Medicare goes along with the AMA and designates obesity as a disease, doctors who discuss weight with their patients will be able to add that diagnosis code to their bill, and charge more for the visit.

Obesity researchers and doctors also defend what appear to be financial conflicts of interest. In 2013, the New England Journal of Medicine published “Myths, Presumptions, and Facts About Obesity.” The authors dismissed the often-observed link between weight cycling and mortality, saying it was “probably due to confounding by health status” (code for “We just can’t believe this could be true”) and went on to plug meal replacements like Jenny Craig, medications, and bariatric surgery.

Five of the 20 authors disclosed financial support from sponsors in related industries, including UAB’s David Allison. I asked him how he would respond to allegations of financial self-interest. “It would be no different than anybody saying about any other person who puts forth an idea, ‘I want to comment that you have this background or personality, this sexual orientation, weight, gender, or race,’ ” he argued. “These conflicts were disclosed, we didn’t hide them, we weren’t ashamed of them. And what’s your point?”

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Another layer to the onion may lie in our deeply held cultural assumptions around weight. “People, journalists, and researchers live in a world where it’s taken for granted that fat is bad and thin is good,” says Saguy.

Doctors buy into those assumptions and biases even more heavily than the rest of us, which may explain in part why they continue to blame patients who can’t keep weight off. Joseph Majdan, a cardiologist who teaches at Jefferson Medical College in Philadelphia, has lost and regained the same 100 or so pounds more times than he can count. Some of the meanest comments Majdan has heard about his weight have come from other doctors, like the med-school classmate who asked if she could project slides onto a pair of his white intern’s pants for a skit. Or the colleague who asked him, “Aren’t you disgusted with yourself?”

“When a person has recurrent cancer, the physician is so empathetic,” says Majdan. “But when a person regains weight, there’s disgust. And that is morally and professionally abhorrent.”

The idea that obesity is a choice, that people who are obese lack self-discipline or are gluttonous or lazy, is deeply ingrained in our public psyche. And there are other costs to this kind of judgmentalism. Research done by Lenny Vartanian, a psychologist at the University of New South Wales, suggests that people who believe they’re worthless because they’re not thin, who have tried and failed to maintain weight loss, are less likely to exercise than fat people who haven’t strongly internalized weight stigma.

It’s hard to think of any other disease—if you want to call it that—where treatment rarely works and most people are blamed for not “recovering.”

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Over the years, Robin Flamm, a full-time parent from Portland, Oregon, has bounced in and out of Weight Watchers and Overeaters Anonymous, gone paleo, done Medifast. Everything worked—for a while. She’d lose 30 pounds and gain back 35, lose 35 and regain 40. She thought she needed to exercise more, eat less, work harder. Like most of us, she blamed herself.

At age 48, she decided she’d spent enough time hating her body, wishing herself different, feeling like a failure. She started seeing a therapist who offers an approach called Health at Every Size, though she was skeptical at first. In the current “obesity epidemic” climate, the idea of pursuing health separate from weight, of accepting that people come in many shapes and sizes, feels radical.

She felt both terrified and relieved to put away her scale, delete her calorie-counting app, and start to rethink her beliefs around food and health. While most obesity docs insist that restrained eating—counting calories or points or exchanges—is necessary for good health, not everyone agrees. About 10 years ago, Ellyn Satter, a dietitian and therapist in Madison, Wisconsin, developed a concept she calls eating competence, which encourages internal self-regulation about what and how much to eat rather than relying on calorie counts or lists of “good” and “bad” foods. Competent eaters, says Satter, enjoy food; they’re not afraid of it. And there’s solid evidence that competent eaters score better on cardiovascular risk markers like total cholesterol, blood pressure, and triglycerides than non-competent eaters.

Not that abiding by competent eating, which fits the Health at Every Size paradigm, is easy; Robin Flamm would tell you that. When her clothes started to feel a little tighter, she panicked. Her first impulse was to head back to Weight Watchers. Instead, she says, she asked herself if she was eating mindfully, if she was exercising in a way that gave her pleasure, if she, maybe, needed to buy new clothes. “It’s really hard to let go of results,” she says. “It’s like free falling. And even though there’s no safety net ever, really, this time it’s knowing there’s no safety net.”

One day she was craving a hamburger, a food she wouldn’t typically have eaten. But that day, she ate a hamburger and fries for lunch. “And I was done. End of story,” she says, with a hint of wonder in her voice. No cravings, no obsessing over calories, no weeklong binge-and-restrict, no “feeling fat” and staying away from exercise. She ate a hamburger and fries, and nothing terrible happened. “I just wish more people would get it,” she says.

Photo illustrations by Juliana Jiménez. Photos by Thinkstock.