Personal Health

Fat: What the Experts Don't Know About Obesity

A recent documentary shows how fat prejudice is keeping even some doctors from understanding obesity.

This article originally appeared onHealth Beat.

The film opens with a fetching redhead puffing away on a treadmill. She's perspiring, but she's smiling gamely into the camera.

"It's not an average workout, but I wasn't an average weight," she explains. "I have to do above and beyond what any of you guys would have to do. I have to try twice as hard, sometimes three times as hard -- just to maintain this level of ... chubbiness."

And she is right. She is chubby. By 21st century mainstream (and magazine) standards of beauty, this young woman is probably 30 pounds overweight. The dimples, the ponytail, the strawberries-and-cream complexion and the undeniable on-camera charisma make her very appealing. But there is no doubt that most physicians would urge her to lose weight. 

Later in the film, we learn that she exercises three hours a day. And when her mother was dying of cancer, this thirtysomething nursed her and learned a great deal about nutrition. Dedicated and determined, she eats healthy meals and sticks to a strict exercise regime.  Why, then, is she "chubby?"

Doctors don't know. That is one of the first things you learn in Fat: What No One is Telling You, a 2007 documentary that is, by turns, entertaining, moving and eye-opening. (The PBS home video, directed by Andrew Fredericks, can be rented on or purchased on

The questions are endless, a narrator tells the audience. "Is it her genes, her childhood, a flaw in her character, stress, sadness, a lost love, processed food, television, seductive advertising, lack of sleep, a government that subsidizes corn, sugar and beef?"

All of the above may well contribute. But taken together, they still don't constitute an answer. Doctors cannot help the vast majority of obese people lose weight -- and keep it off -- because doctors don't know what causes obesity.

"If It Were That Simple…"      

Although many physicians still "believe that obesity is caused by eating too much and not exercising enough, such thinking is too simplistic," says Dr. Robert Lustig, of the Division of Pediatric Endocrinology at the University of California, San Francisco. An expert in the field, he knows that obesity is "a chronic condition." And we don't have a cure.

This is why, even when patients enter medically supervised weight-loss programs and stick with the rules, Lustig explains, 95 percent regain whatever pounds they lose. 

"This is not simply ‘energy in and energy out.' If it were, we would have solved it a long time ago," says Harvard's Dr. Lee Kaplan, who heads the Weight Reduction Program at Massachusetts General Hospital and has established a new, comprehensive basic and clinical research program.

"Obesity doesn't seem like a subtle disease," adds Kaplan, who appears in the documentary. "But it is. If something is off kilter by just 1 percent in your system, that can lead to a 100-pound weight gain.More than 400 genes are involved in weight regulation. And that doesn't include the environmental factors."

Fat goes on to introduce us to a very bright 300-pound 18-year-old who has sought medical help, researched obesity and, with the support of his doctor, is now planning on bariatric surgery (a.k.a. "stomach-stapling"). "They just haven't figured out this obesity thing," he says. "There is something haywire in your body.

"You become depressed when you realize that … you're going to die earlier. And when they bury you, they'll need 20 people to carry you rather than four." 

Obesity is "indescribably complex," he adds. In his own family, it is a mystery: "My twin sister is skinny. I'm not. When we were born, we were the same weight and length.  But many people in the family are overweight, which suggests a genetic component."

Another person in the film was not heavy as a child. "A tomboy, I was always very athletic," this young woman says. And the pictures of her as an adolescent confirm that she was an extremely attractive female athlete. No fat -- just great muscle tone. But then "I moved into the corporate world," she explains.  "And since I've been at Microsoft, I've gained 125 pounds."

As an executive, she travels frequently, and, "If I'm traveling coach, it's really tight. Last time, I was in a center seat, and kept apologizing to the people next to me. They were squished, but very nice about it," she says, still obviously terribly embarrassed by the memory.

Many young athletes move into the corporate world and don't gain 125 pounds. Why would a young woman who loved sports suddenly find herself too heavy to play? This is the conundrum that medicine hasn't cracked. Meanwhile, this Microsoft executive would do anything to lose weight. 

"I hate this," she says. "I can no longer do the things I love to do." She and her husband (who is also a very big man) haven't been able to get pregnant. To try to solve their problem, they have signed up for a comprehensive (and no doubt expensive) program that includes doctors, nutritionists and trainers.

They have purchased health cook books, and admit that they really don't know how to cook. "I have no idea how to cook chicken," she acknowledges.

"What is chicken?" her husband asks, only half-joking.

But, she tells her husband, "We'll just have to try these recipes. Some of them we'll hate -- so we won't cook them again." She is hopeful that they will find others that they like.


"Fat prejudice is the primary impediment to understanding -- or wanting to understand what obesity is all about," says a public health nurse who appears in Fat.

Physicians know too little about what causes obesity in part because, as this nurse points out, "blaming the victim has stood in the way of understanding." Here, I am reminded of how, in the past, we blamed patients suffering from depression and other forms of mental illness. For centuries, this prejudice stood in the way of understanding that mood disorders are caused by a flaw in chemistry, not character

In Fat, patients describe how even some doctors treat them with contempt: "When I went to get a Pap smear, the doctor said, ‘You're too fat; come back when you've lost weight,' " one woman recalls. 

The documentary also points out that "while everyone dies ... it should perhaps come as no surprise that in our society, obese people are blamed for dying. If a thin patient comes into the hospital, has a heart attack and dies, cause of death is labeled ‘heart disease,' " says a public health nurse in the film. "If an obese patient has a heart attack and dies, cause of death is 'obesity.' "

Conventional wisdom says that if you put too much food in your mouth and don't exercise enough, you'll wind up fat. Period. As is so often the case, the conventional wisdom is wrong. Experts report that some people eat rich, fatty foods, never exercise and remain thin. Others exercise daily, diet religiously and are seriously overweight. Of course many overweight people who need to lose 20 or 25 pounds take it off and keep it off. But they are not obese -- they are not fighting a chronic condition.

Medical science has not yet sliced through the tangle of genetic, metabolic, social, psychological and environmental factors that cause obesity.

Nevertheless, scientists today have begun to look past the old-fashioned notion that obesity is merely a matter of gluttony and have made real progress in beginning to understand a terribly complicated chronic disease.

A Unique Disease -- the Body Undermines the Cure

What we do know is that "Obesity is the one disease where your body fights the cure," saysDr. Michael Rosenbaum, a Columbia University researcher working on an National Institutes of Health-funded study on weight control.

By and large, the body is programmed to help you heal. But not in this case. People think that dieting is a matter of choice, saysArthur Frank, medical director of the George Washington University Weight Management Program. But in fact, losing weight requires overcoming powerful brain signals that are working against you.

If you have ever dieted, you may already know that, once you lose some weight, your metabolism slows down and you burn fewer calories. For all your body knows, you are stranded on a desert island, starving to death. So it tries to "help." The brain is wired to eat and store fat to protect against starvation. In fact, when you lose weight, the human body has redundant systems to try to save you. That's how the human species has survived.

In "Wired to Eat," a 2005 article published in MIT Technology Review, Jeffrey Friedman, an obesity researcher at Rockefeller University, explainsthat the mechanism that drives us to eat is located in the hypothalamus, at the base of the brain, where two types of neurons appear to be the chief regulators of appetite. These neurons tell us when we're hungry and when we're not. The so-called NPY neuron stimulates hunger, and the POMC inhibits appetite. Each neuron is turned up or down by chemicals that wash over them. "A dominant factor in controlling weight is this basic neural circuit," says Friedman.

The chief chemical involved is leptin, a hormone produced by fat cells in the belly. When people gain weight, fat cells increase the levels of leptin, and as leptin washes over the POMC neuron, their appetite is suppressed. When people start to lose weight, body fat is reduced, which decreases the levels of leptin. Less leptin means the POMC turns down and the NPY neuron predominates, which ramps up hunger. Other chemicals -- fats, sugars and neurotransmitters -- also influence the actions of these neurons, but leptin seems to be the key.

Friedman is famous for his 1994 discovery of the gene that codes for leptin. And for a brief moment in the mid-1990s, the MIT Technology Review explains, "leptin seemed to be a potential wonder cure for obesity." Researchers hoped that a leptin injection would turn up the POMC neuron that inhibits hunger. But leptin injections work for only a small percentage of the obese. It turns out that the majority [of obese people] do produce leptin, but their bodies actually resist the effects of the hormone by blocking its ability to turn up the hunger-suppressing action of the POMC neuron. So their appetites remain large, and they keep eating -- and gaining weight -- until they reach the point at which the resistance stops. Where that point lies, Friedman believes, is determined by genetic makeup.

Some people appear to be hardwired to be particularly ravenous. When access to food is unlimited, say hunger-gene experts,these people can will themselves to eat less, but their efforts will almost inevitably be overridden by the far more powerful force of genetics. Studies show that invariably, weight loss is followed by weight gain, making obesity a lifelong struggle. "You just have to keep falling off the horse and getting back on again," says one woman who appears in the film Fat. A physician in the film points out that trying to continue eating less is like trying to run upstairs without breathing faster. "You can do it for a while, but not for that long."

This explains why appetite suppressants have a minimal effect in helping obese patients, says Dr. Robert Lustig of the Division of Pediatric Endocrinology at the University of California, San Francisco. "These medications become less and less effective after just four months," Lustig explains. This is not because of a lack of compliance on the part of the patient, but rather due to leptin resistance, which persists even in the face of pharmacotherapy. When appetite suppressants foil one set of receptors, another mechanism kicks in, and hunger returns.

Looking for the Needle in a Small Gene Pool        

Rockefeller University's Friedman did some of his most important obesity research on Kosrae, a tiny volcanic island in the Pacific Ocean, some 4,670 kilometers southwest of Hawaii. There, he led a university team that worked in a joint project with the Kosrae state health authorities and the U.S. Department of Health and Human Services to discover why not everyone on the island was overweight.

Until the United States took control of Kosrae and the rest of Micronesia after World War II and began shipping in canned and processed foods, the people of this island were predominately lean -- eating fish, bananas, coconuts and taro. Most islanders lived a near-subsistence life, suffering through frequent droughts and stormy seasons that decimated crops. And they stayed thin.

But after World War II, their diet changed. San Francisco Chronicle reporter David Ewing Duncan visited the island in 2005, and describesgrocery store shelves stocked with "Frosted Flakes, pork and beans, canned peas, soft drinks and Spam ... Today well over half of the adult population is overweight," he observes. This comes as no shock; we know that as environment changes, and foods high in carbs and fat become widely available, an entire population is likely to gain weight.

The surprise is that some on the island remained lean despite the change in diet. And this is what attracted Rockefeller molecular biologists who were searching the human genome for genes and mechanisms that influence how we eat.

This diversity in a small population -- 7,600 people on an isolated island where most people are descended from a few families -- is what intrigued Friedman. Having just a few genetic lineages on the island means that each person's genomic makeup is far more similar to his or her compatriots' than, say, an American's would be.

"Looking for a gene is like searching for a needle in a haystack," he says. "On Kosrae, the small gene pool makes the haystack smaller."

The MIT Technology Review explains Friedman came to believe that the Kosraeans' ballooning weight is a manifestation of what geneticist James Neel in 1962 dubbed the "thrifty gene" theory. Neel posited that in an environment prone to famine, hunter-gatherers gained a selective advantage if their genes predisposed them to storing fat when food was available. Those with such ‘thrifty genes' were more likely to survive famines and pass on their genes. But in modern times, the thrifty gene has proved a liability.

"The theory also posits that people who lived in early agricultural societies, such as those in the Fertile Crescent in the Middle East, had a steady supply of food from plants and domesticated animals and thus didn't need to store fat. So in our world today, people with lean genes are protected from obesity, and those with fat genes are at the mercy of DNA."

Why leptin resistance occurs in some people is poorly understood, Friedman says. It may be a relic of the thrifty-gene response, ramping up appetite in those whose ancestors lacked adequate food. The Rockefeller team measured leptin levels in the Kosraean population; Friedman is using that data to help correlate leptin resistance with genes that might be responsible for it. According to Friedman, each of us has a ‘set point' of hunger and satiation, which we inherited from our individual forebears. "We are born with this setting, and we are driven to keep eating until we reach it."

"People whose ancestors, like most Kosraens', had to work hard to get enough to eat, had their hunger-volume -- analogous to a specific setting on a radio dial -- turned up to 8 or 10." Chronicle reporter Duncan says. "Those whose ancestors had plenty of food -- for instance, the agriculturists of the Fertile Crescent and Europe, and parts of India and China, people who have basically had stable food supplies for as many as 10,000 years -- have inherited a setting of 2 or 3."

Friedman concedes that more work is needed to understand the role of exercise in weight gain. But, according to the MIT Technology Review, he does believe that "the weight increases of the past 20 years in the United States represent a steady progression of people eating enough food to reach their set points, rather than a sudden spike in bad eating habits or more sitting around." What really intrigues Friedman is why everyone doesn't get chubby when there is plenty to eat. Analyses show that the number of lean people has remained steady for the past 30 years, he says. "One's size is not an environmental effect. Nor is it a matter of willpower.'"

There is of course much money to be made if entrepreneurs can convince the obese that they have the secret to weight loss. As Duncan notes, "the diet industry [is] skeptical of Friedman's claim that obesity is as overdetermined [as he claims. The industry] insists that people can overcome the hunger impulse and trim down with healthy diets and reduced calories. Friedman says this is true, but that even a heavy person in most cases can lose only 10 or 20 pounds and keep it off. But even a small amount of weight loss can be healthy, he says. ‘You can lose more for a period of time,' he says, but the biology will eventually force you to eat in most cases, and ‘you will regain the weight.'

"Friedman acknowledges that what he suggests is counterintuitive, since people can resist jelly beans up to a point. But he insists that, for the majority of the obese, free will in weight control is an illusion. ‘This is a way of thinking that needs to change.' "

One might wonder why the thrifty gene has survived. After all, how many Americans die because they don't get enough food? Granted, many of America's poor are malnourished, which in turn leads to diseases that can be fatal, but few succumb because they simply can't get enough calories.

But as the documentary Fat points out, Americans "have gone from having very little to eat to being able to eat a lot -- with a few bucks in our pocket -- in just 75 years."

Panning a fast-food restaurant, the film points out how many calories you can get for just $4. This wasn't true during the Great Depression of the 1930s. Indeed, the film's narrator observes "there are millions of people who are here today who wouldn't have been here 60 years ago," because they couldn't have "gotten this much food for that amount of money in yesterday's dollars." 

Little wonder that the brain still sounds an alarm when we lose weight.

What We Are Learning From Gastric Bypass Surgery

And leptin resistance is just one of many mechanisms that protects us.

"The gut has a nervous system -- and a mind of its own -- that decides what and how much we eat," says Michael Gershon, a bowel expert at Columbia University and author of the 1998 book The Second Brain, who appears in Fat.

At Massachusetts General, Dr. Lee Kaplan agrees: "We have two brains -- in the stomach and ‘upstairs.' The brain in the gut can disturb the brain in the head."

"Neurochemical signals flow between the two brains," Kaplan says, "And we have discovered that gastric bypass surgery interrupts that flow."

Until recently, physicians believed that patients lost weight because the surgery reduced the size of the stomach, forcing them to eat less. But once again, it's not that simple. Researchers performing gastric bypass surgery on rats have discovered that the surgery severs nerves in the bowel that communicate with the brain -- and that this is tied to weight loss.

Today, the surgery is giving researchers valuable new information about how the brain and gut manage obesity.

"In the next 5 or 10 years, we'll find that there are many, many other things we didn't know," Kaplan predicts. "Gastric bypass surgery is not a solution for obesity -- it's only appropriate for the sickest of our patients," he adds. "But it's given us an enormous hope that, through what we learn, we'll be able to solve the problem."


By the end of the film, the 300-pound 18-year-old had his bariatric surgery and, to his delight, lost 147 pounds. "I’m a whole human less in weight," he exulted.  

Indeed, he had lost the equivalent of his skinny twin’s total weight. (It’s worth noting that this surgery is recommended only as a last resort. And even then, a patient should make sure that his physician is an experienced bariatric surgeon who has performed many operations. The risks are real -- and harrowing. Nevertheless, for this young man, the procedure was a huge success.)

What about the former tomboy who gained 125 pounds after becoming an executive at Microsoft? Humiliated when she spilled out of her airplane seat and onto her fellow passengers, and frustrated that she could no longer participate in the sports she loved, she became even more depressed when she had difficulty getting pregnant.  

That’s when she and her oversized husband signed up for a comprehensive program that includes doctors, nutritionists and trainers.

By the time the film was completed, they were still exercising and dieting, though they hadn’t lost much weight. Many obese people find it all but impossible to lose weight and keep it off. Their body fights every attempt to shed pounds as neurological signals flowing from their gut to their brain overrides their conscious will. Thanks to genes that we are only beginning to understand, they are hardwired to maintain a certain weight.

This is what makes obesity a chronic disease -- and a lifelong struggle. Nevertheless, this couple wasn’t giving up.

"You just have to keep on falling off the horse, and getting back on," said the former athlete. And recognizing this fact is half the battle. 

The good news is that, by the end of the film, the couple were finally pregnant. The delighted mother-to-be expressed her determination to try to remain as healthy as possible. Having a child will, no doubt, motivate her to keep on exercising.

And when it comes to better health, exercise may well be much more important than trying to achieve the svelte figure that society holds in such high esteem. A U.K. study presented at the Society of Behavioral Medicine Scientific Meeting in Cambridge in 2006 tells the tale.

The yearlong study of 62 women ages 24 to 55 encouraged them not to diet but to take part in exercise classes. They were required to do four hours a week of exercise such as tai chi, aqua aerobics or circuit classes. The program also included educational sessions teaching the women how to read food labels as well as behavioral therapy to help the women respond to body cues such as hunger and feeling full. But the women were encouraged to eat whatever they wanted, in moderation.

The women who took part in the study all had a body mass index over 30, which is classed as clinically obese. After a year, the average participant had lost very little weight.  But the women were significantly fitter and happier with themselves. Blood pressure, heart rate and cholesterol fell, and respiratory fitness increased. The women also felt better in terms of general well-being, body image, self-perception and stress. 

"People of all sizes and shapes can reduce the risk of poor health by adopting a healthier lifestyle," Dr. Erika Borkoles, exercise psychologist at Leeds Metropolitan University told the BBC. "Health care professionals need to shift their focus from weight loss to helping their patients improve their health."

Borkoles said the program, which has been set up with Leeds City Council, gave the women discounts to continue exercise classes after the 12-month project finished.

Dr. David Haslam, clinical director of the National Obesity Forum, confirmed the study’s findings: "It is quite well known that you can improve your lifestyle and reduce your risk of cancer, stroke and heart disease. You can improve fitness without losing weight, as you can gain muscle and lose fat and weigh the same or even gain weight."

But he disagreed about shifting focus from weight loss to exercise. "It's important to think across the board."

Nevertheless, for those who cannot lose weight, "Exercise without weight loss is an effective strategy for obesity reduction" according to a study published in the Journal of Applied Physiology in 2005.

What exactly does "obesity reduction without weight loss" mean? The obese men in the study who participated in aerobic exercise five times per week for 60 minutes did not shed pounds. The study was designed to make sure that they wouldn’t: "To allow us to test the hypothesis that significant obesity reduction could occur despite the absence of change in body weight, all subjects were asked to maintain body weight, and they consumed the calories required to compensate for the energy expended during the exercise sessions," the researchers explain.

Nevertheless, the obese men and the control group of lean men who participated in the study watched their waist circumferences shrink. Cardiorespiratory fitness increased in both groups, as did skeletal muscle, with total fat reduced. These changes were roughly equal in both groups. But when it came time to measure abdominal fat, reductions in the obese group were significantly greater.

The researchers acknowledge that the levels of fat loss observed in this study are less than those generally observed in response to exercise-induced weight loss that includes dieting.

"This reinforces current guidelines [that a combination of exercise and eating fewer calories] is the principal therapy for overweight and obese individuals ..." they observed. "However, the findings here extend these guidelines and provide substantial support for the recommendation that exercise without weight loss represents another strategy for obesity reduction.

"This is good news," they conclude, "and may be used to encourage and counsel those who appear resistant to substantial weight loss despite considerable effort. Stated differently, health care professionals should recognize that exercise without weight loss is not a failure when obesity reduction is the desired outcome. To the contrary, combined with the knowledge that exercise is associated with substantial health benefits independent of obesity, exercise without weight loss is a useful strategy for reducing obesity and related comorbid conditions: a win-win scenario."

I would add only that our obsession with whether or not people meet cultural norms for beauty -- rather than whether they are happy and healthy -- fuels the prejudice against obesity that can make even physicians cruel when their patients fail to lose weight.

As the public health nurse in the film Fat observes: "These are free-range fat people, just trying to do their best in a culture that hates them."

At the end of Fat, we return to the charismatic redhead who we saw at the beginning, puffing away on a treadmill. As the film closes, she’s still on the treadmill, mopping her brow with a towel.

"Sometimes I wonder, why the hell am I doing this to myself?" she confesses. "Can’t I just be happy with who I am?" She explains that part of why she exercises so relentlessly is "for my career. I’m in TV -- I have to look good. And so I associate myself with the number I see on the scale. I don’t know of that’s right or wrong, but it just is."

She blames herself: "How can I ever be happy unless I can control what I put in my mouth? On the inside, I may feel like I’m a good person. But what people see from the outside -- it stops people."

Maggie Mahar is a fellow at the Century Foundation and the author of Money-Driven Medicine: The Real Reason Health Care Costs So Much (Harper/Collins 2006).
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