How Obesity Became a Disease

And, as a consequence, how weight loss became an industry

Weight loss is a big business, and, since it’s rarely successful in the long term, it comes with a built-in supply of repeat customers. And doctors have been involved in the business one way or another for a long time. Some 2,000 years ago, the Greek physician and philosopher Galen diagnosed “bad humors” as the cause of obesity, and prescribed massage, baths, and “slimming foods” like greens, garlic, and wild game for his overweight patients. More recently, in the early 20th century, 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, the weight-loss chemical 2,4-dinitrophenol (DNP) came along, followed by amphetamines, diuretics, laxatives, and diet pills like fen-phen, all of which worked only in the short term and caused side effects ranging from the annoying to the fatal.

The national obsession with weight got a big boost in 1942, when a life-insurance company created a set of tables that became the most widely referenced standard for weight in North America. The Metropolitan Life Insurance Company crunched age, weight, and mortality numbers from nearly 5 million policies in the United States and Canada 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, using increasingly clinical-sounding terms like adipose, overweight, and obese. The new terminology reinforced the idea that only doctors should and could treat weight issues. The word overweight, for example, implies excess; to be overweight suggests you’re over the “right” weight. The word obese, from the Latin obesus, or “having eaten until fat,” handily conveys both a clinical atmosphere and that oh-so-familiar sense of moral judgment.

By the 1950s, even as Hollywood glamorized voluptuous actresses like Marilyn Monroe and Elizabeth Taylor, medicine was taking a different stance. In 1952, Norman Jolliffe, the director of New York’s Bureau of Nutrition, warned doctors at the annual meeting of the American Public Health Association that “a new plague, although an old disease, has arisen to smite us.” He estimated that 25 to 30 percent of the American population at the time was overweight or obese, a number he essentially made up. “No one loves a fat girl except possibly a fat boy, and together they waddle through life with a roly-poly family,” wrote Paul Craig, a physician from Tulsa, Oklahoma, in 1955. Craig was enthusing over a 1907 study that claimed “gratifying results … on the problem of obesity” by putting people on 800-calories-a-day diets and dosing them liberally with amphetamines, phenobarbital, and methylcellulose. (Craig concluded, in a comment that fails to inspire confidence in his methods of scientific inquiry, “Not all people who eat gluttonously grow fat, but no fat man or woman eats, as they claim, like a bird, unless they refer to a turkey buzzard.”)

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. Through annual conferences like the first International Congress on Obesity, held in Bethesda, Maryland, in 1973, doctors helped propagate the idea that dealing with weight was a job for highly trained experts. “Medical professionals intentionally made a case that fatness was a medical problem, and therefore the people best equipped to intervene and express opinions about it were people with M.D.s,” says Abigail Saguy, a sociologist at the University of California, Los Angeles.

Those medical experts believed that “any level of thinness was healthier than being fat,” writes Nita Mary McKinley, a professor of psychology at the University of Washington, Tacoma. This attitude inspired a number of new treatments for obesity, including stereotactic surgery, also known as psychosurgery, which involved burning lesions into the hypothalamuses of people with “gross obesity.” Jaw wiring was another invasive procedure that gained traction in the 1970s and 1980s. It quickly fell out of favor, maybe because it stopped working the minute people started eating again. (At least one dentist in Brooklyn still promotes it.)

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On a cool June afternoon in 2013, hundreds of doctors from around the country streamed into the grand ballroom of the Hyatt Regency Chicago. They were there, on day three of the American Medical Association’s annual meeting, to vote on a list of organization policies—boring but necessary stuff, for the most part. But one item on the ballot that day would prove contentious, and not just within the paneled walls of the ballroom. Resolution 420 was short and to the point: “That our American Medical Association recognize obesity as a disease state with multiple pathophysiological aspects requiring a range of interventions to advance obesity treatment and prevention.”

The question—whether to classify obesity as a disease in and of itself, or continue to consider it a risk factor for diseases like type 2 diabetes—had been under discussion for years, both within the organization and outside it. Months earlier, the AMA asked its own Committee on Science and Public Health to explore the issue; the committee came up with a five-page opinion suggesting that obesity should not be officially labeled as a disease, for several reasons.

For one thing, the committee said, obesity doesn’t fit the definition of a medical disease. It has no symptoms, and it’s not always harmful—in fact, for some people in some circumstances, it’s been known to be protective rather than destructive.

For another, a disease, by definition, involves the body’s normal functioning gone wrong. But many experts think obesity—the body efficiently storing calories as fat—is a normal adaptation to a set of circumstances (periods of famine) that’s held true for much of human history. In that case, the bodies that tend toward obesity aren’t diseased; they’re actually more efficient than naturally lean bodies. True, we live in a time when food is more abundant for most people and life is more sedentary than it used to be, and we don’t have the same need to store fat. But that simply means the environment has changed faster than we can adapt.

Finally, the committee worried that medicalizing obesity could potentially hurt patients, creating even more stigma around weight and pushing people into unnecessary—and ultimately useless—“treatments.”

The AMA membership didn’t agree with the committee; they passed Resolution 420 in an overwhelming voice vote. I asked the organization’s president, Ardis Hoven, an internist who specializes in infectious diseases, to help me understand why the membership voted that way despite the committee’s recommendation. She wouldn’t talk to me directly, instead writing through a spokesperson, “The AMA has long recognized obesity as a major public-health concern, but the recent policy adopted in June marks the first time we’ve recognized obesity as a disease due to the prevalence and seriousness of obesity.”

There are, of course, other possible explanations for the AMA’s decision. As James Hill, the director of the Anschutz Health and Wellness Center at the University of Colorado, told ABC, “Now we start getting some standardization for reimbursement and treatments.”

In other words, follow the money. Doctors want to be paid for delivering weight-loss treatments to patients. Coding office visits for Medicare, for instance, is a complex process that involves counting the number of bodily systems reviewed and the number of diseases counseled for. If Medicare goes along with the AMA and designates obesity as a disease, doctors who even mention weight to their patients could charge more for the same visit than doctors who don’t.

But that’s trivial compared with the sorts of financial conflicts of interest defended by some in the field. It’s rare to find an obesity researcher who hasn’t taken money from industry, whether it’s pharmaceutical companies, medical-device manufacturers, bariatric-surgery practices, or weight-loss programs. The practice isn’t limited to lesser-known luminaries, either. In 1997, a panel of nine medical experts tapped by the National Institutes of Health voted to lower the BMI cutoff for overweight from 27 (28 for men) to 25. Overnight, millions of people became overweight, at least according to the NIH. The panel argued that the change brought BMI cutoffs in line with World Health Organization Criteria, and that a “round” number like 25 would be easy for people to remember.

What they didn’t say, because they didn’t have to, is that lowering BMI cutoffs, and putting more people into the overweight and obese categories, also made more people eligible for treatment.

This article has been adapted from Harriet Brown's book Body of Truth: How Science, History, and Culture Drive Our Obsession With Weight—and What We Can Do About It.