JOIN USSad story: Why fat people can't lose weight easily
For 15 years, Joseph Proietto has been helping people lose weight. When these obese patients arrive at his weight-loss clinic in Australia, they are determined to slim down.
And most of the time, he says, they do just that, sticking to the clinic’s programme and dropping excess pounds. But then, almost without exception, the weight begins to creep back. In a matter of months or years, the entire effort has come undone, and the patient is fat again.
“It has always seemed strange to me,” says Proietto, who is a physician at the University of Melbourne. “These are people who are very motivated to lose weight, who achieve weight loss most of the time without too much trouble and yet, inevitably, gradually, they regain the weight.”
Anyone who has ever dieted knows that lost pounds often return, and most of us assume the reason is a lack of discipline or a failure of willpower. But Proietto suspected that there was more to it, and he decided to take a closer look at the biological state of the body after weight loss.
Beginning in 2009, he and his team recruited 50 obese men and women. The men weighed an average of 233 pounds; the women weighed about 200 pounds. Although some people dropped out of the study, most of the patients stuck with the extreme low-calorie diet, which consisted of special shakes called Optifast and two cups of low-starch vegetables, totaling just 500 to 550 calories a day for eight weeks. Ten weeks in, the dieters lost an average of 30 pounds.
At that point, the 34 patients who remained stopped dieting and began working to maintain the new lower weight. Nutritionists counselled them in person and by phone, promoting regular exercise and urging them to eat more vegetables and less fat. But despite the effort, they slowly began to put on weight. After a year, the patients already had regained an average of 11 of the pounds they struggled so hard to lose. They also reported feeling far more hungry and preoccupied with food than before they lost the weight.
While researchers have known for decades that the body undergoes various metabolic and hormonal changes while it’s losing weight, the Australian team detected something new. A full year after significant weight loss, these men and women remained in what could be described as a biologically altered state.
Their still-plump bodies were acting as if they were starving and were working overtime to regain the pounds they lost. For instance, a gastric hormone called ghrelin, often dubbed the ‘hunger hormone,’ was about 20 per cent higher than at the start of the study. Another hormone associated with suppressing hunger, peptide YY, was also abnormally low. Levels of leptin, a hormone that suppresses hunger and increases metabolism, also remained lower than expected. A cocktail of other hormones associated with hunger and metabolism all remained significantly changed compared to pre-dieting levels. It was almost as if weight loss had put their bodies into a unique metabolic state, a sort of post-dieting syndrome that set them apart from people who hadn’t tried to lose weight in the first place.
“What we see here is a coordinated defence mechanism with multiple components all directed toward making us put on weight,” Proietto says. “This, I think, explains the high failure rate in obesity treatment.”
While the findings from Proietto and colleagues, published this fall in The New England Journal of Medicine, are not conclusive — the study was small and the findings need to be replicated — the research has nonetheless caused a stir in the weight-loss community, adding to a growing body of evidence that challenges conventional thinking about obesity, weight loss and willpower.
For years, the advice to the overweight and obese has been that we simply need to eat less and exercise more. While there is truth to this guidance, it fails to take into account that the human body continues to fight against weight loss long after dieting has stopped. This translates into a sobering reality: once we become fat, most of us, despite our best efforts, will probably stay fat.
I have always felt perplexed about my inability to keep weight off. I know the medical benefits of weight loss, and I don’t drink sugary sodas or eat fast food. I exercise regularly — a few years ago, I even completed a marathon. Yet during the 23 years since graduating from college, I’ve lost 10 or 20 pounds at a time, maintained it for a little while and then gained it all back and more, to the point where I am now easily 60 pounds overweight.
Healthy and unhealthy diets
I wasn’t overweight as a child, but I can’t remember a time when my mother, whose weight probably fluctuated between 150 and 250 pounds, wasn’t either on a diet or, in her words, cheating on her diet. Sometimes we ate healthful, balanced meals; on other days dinner consisted of a bucket of Kentucky Fried Chicken.
As a high-school cross-country runner, I never worried about weight, but in college, when my regular training runs were squeezed out by studying and socialising, the numbers on the scale slowly began to move up. As adults, my three sisters and I all struggle with weight, as do many members of my extended family. My mother died of esophageal cancer six years ago. It was her great regret that in the days before she died, the closest medical school turned down her offer to donate her body because she was obese.
It’s possible that the biological cards were stacked against me from the start. Researchers know that obesity tends to run in families, and recent science suggests that even the desire to eat higher-calorie foods may be influenced by heredity. But untangling how much is genetic and how much is learned through family eating habits is difficult. What is clear is that some people appear to be prone to accumulating extra fat while others seem to be protected against it.
In a seminal series of experiments published in the 1990s, the Canadian researchers Claude Bouchard and Angelo Tremblay studied 31 pairs of male twins ranging in age from 17 to 29, who were sometimes overfed and sometimes put on diets. (None of the twin pairs were at risk for obesity based on their body mass or their family history.)
In one study, 12 sets of the twins were put under 24-hour supervision in a college dormitory. Six days a week they ate 1,000 extra calories a day, and one day they were allowed to eat normally. They could read, play video games, play cards and watch television, but exercise was limited to one 30-minute daily walk. Over the course of the 120-day study, the twins consumed 84,000 extra calories beyond their basic needs.
That experimental binge should have translated into a weight gain of roughly 24 pounds (based on 3,500 calories to a pound). But some gained less than 10 pounds, while others gained as much as 29 pounds.
The amount of weight gained and how the fat was distributed around the body closely matched among brothers, but varied considerably among the different sets of twins. Some brothers gained three times as much fat around their abdomens as others, for instance. When the researchers conducted similar exercise studies with the twins, they saw the patterns in reverse, with some twin sets losing more pounds than others on the same exercise regimen. The findings, the researchers wrote, suggest a form of ‘biological determinism’ that can make a person susceptible to weight gain or loss.
But while there is widespread agreement that at least some risk for obesity is inherited, identifying a specific genetic cause has been a challenge. In October 2010, the journal Nature Genetics reported that researchers have so far confirmed 32 distinct genetic variations associated with obesity or body-mass index. One of the most common of these variations was identified in April 2007 by a British team studying the genetics of Type 2 diabetes.
According to Timothy Frayling at the Institute of Biomedical and Clinical Science at the University of Exeter, people who carried a variant known as FTO faced a much higher risk of obesity — 30 per cent higher if they had one copy of the variant; 60 per cent if they had two.
“After you’ve lost weight, your brain has a greater emotional response to food,” Rosenbaum says. “You want it more, but the areas of the brain involved in restraint are less active.” Combine that with a body that is now burning fewer calories than expected, he says, “and you’ve created the perfect storm for weight regain.” How long this state lasts isn’t known, but preliminary research at Columbia suggests that for as many as six years after weight loss, the body continues to defend the old, higher weight by burning off far fewer calories than would be expected.
The problem could persist indefinitely. (The same phenomenon occurs when a thin person tries to drop about 10 percent of his or her body weight — the body defends the higher weight.) This doesn’t mean it’s impossible to lose weight and keep it off; it just means it’s really, really difficult.
Nobody wants to be fat. In most modern cultures, even if you are healthy — in my case, my cholesterol and blood pressure are low and I have an extraordinarily healthy heart — to be fat is to be perceived as weak-willed and lazy. It’s also just embarrassing. Once, at a party, I met a well-respected writer who knew my work as a health writer. “You’re not at all what I expected,” she said, eyes widening. The man I was dating, perhaps trying to help, finished the thought. “You thought she’d be thinner, right?” he said. I wanted to disappear, but the woman was gracious. “No,” she said, casting a glare at the man and reaching to warmly shake my hand. “I thought you’d be older.”
Rethinking biases
If anything, the emerging science of weight loss teaches us that perhaps we should rethink our biases about people who are overweight. It is true that people who are overweight, including myself, get that way because they eat too many calories relative to what their bodies need. But a number of biological and genetic factors can play a role in determining exactly how much food is too much for any given individual. Clearly, weight loss is an intense struggle, one in which we are not fighting simply hunger or cravings for sweets, but our own bodies.
The view of obesity as primarily a biological, rather than psychological, disease could also lead to changes in the way we approach its treatment. Scientists at Columbia have conducted several small studies looking at whether injecting people with leptin, the hormone made by body fat, can override the body’s resistance to weight loss and help maintain a lower weight. In a few small studies, leptin injections appear to trick the body into thinking it’s still fat. After leptin replacement, study subjects burned more calories during activity. And in brain-scan studies, leptin injections appeared to change how the brain responded to food, making it seem less enticing. But such treatments are still years away from commercial development. For now, those of us who want to lose weight and keep it off are on our own.
One question many researchers think about is whether losing weight more slowly would make it more sustainable than the fast weight loss often used in scientific studies. Leibel says the pace of weight loss is unlikely to make a difference, because the body’s warning system is based solely on how much fat a person loses, not how quickly he or she loses it. Even so, Proietto is now conducting a study using a slower weight-loss method and following dieters for three years instead of one.
Given how hard it is to lose weight, it’s clear, from a public-health standpoint, that resources would best be focused on preventing weight gain. The research underscores the urgency of national efforts to get children to exercise and eat healthful foods.
But with a third of the US adult population classified as obese, nobody is saying people who already are very overweight should give up on weight loss. Instead, the solution may be to preach a more realistic goal. Studies suggest that even a 5 per cent weight loss can lower a person’s risk for diabetes, heart disease and other health problems associated with obesity. There is also speculation that the body is more willing to accept small amounts of weight loss.
But an obese person who loses just 5 percent of her body weight will still very likely be obese. For a 250-pound woman, a 5 percent weight loss of about 12 pounds probably won’t even change her clothing size. Losing a few pounds may be good for the body, but it does very little for the spirit and is unlikely to change how fat people feel about themselves or how others perceive them.