[meteeratymn]

The Fat Trap
By TARA PARKER-POPE
Published: December 28, 2011 in The NY Times
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 program 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.”

An interview with Tara Parker-Pope on her cover story on weight loss.

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 counseled 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 percent 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 defense 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.

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 socializing, 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 percent higher if they had one copy of the variant; 60 percent if they had two.

This FTO variant is surprisingly common; about 65 percent of people of European or African descent and an estimated 27 to 44 percent of Asians are believed to carry at least one copy of it. Scientists don’t understand how the FTO variation influences weight gain, but studies in children suggest the trait plays a role in eating habits. In one 2008 study led by Colin Palmer of the University of Dundee in Scotland, Scottish schoolchildren were given snacks of orange drinks and muffins and then allowed to graze on a buffet of grapes, celery, potato chips and chocolate buttons. All the food was carefully monitored so the researchers knew exactly what was consumed. Although all the children ate about the same amount of food, as weighed in grams, children with the FTO variant were more likely to eat foods with higher fat and calorie content. They weren’t gorging themselves, but they consumed, on average, about 100 calories more than children who didn’t carry the gene. Those who had the gene variant had about four pounds more body fat than noncarriers.

I have been tempted to send in my own saliva sample for a DNA test to find out if my family carries a genetic predisposition for obesity. But even if the test came back negative, it would only mean that my family doesn’t carry a known, testable genetic risk for obesity. Recently the British television show “Embarrassing Fat Bodies” asked Frayling’s lab to test for fat-promoting genes, and the results showed one very overweight family had a lower-than-average risk for obesity.

A positive result, telling people they are genetically inclined to stay fat, might be self-fulfilling. In February, The New England Journal of Medicine published a report on how genetic testing for a variety of diseases affected a person’s mood and health habits. Over all, the researchers found no effect from disease-risk testing, but there was a suggestion, though it didn’t reach statistical significance, that after testing positive for fat-promoting genes, some people were more likely to eat fatty foods, presumably because they thought being fat was their genetic destiny and saw no sense in fighting it.

While knowing my genetic risk might satisfy my curiosity, I also know that heredity, at best, would explain only part of why I became overweight. I’m much more interested in figuring out what I can do about it now.

The National Weight Control Registry tracks 10,000 people who have lost weight and have kept it off. “We set it up in response to comments that nobody ever succeeds at weight loss,” says Rena Wing, a professor of psychiatry and human behavior at Brown University’s Alpert Medical School, who helped create the registry with James O. Hill, director of the Center for Human Nutrition at the University of Colorado at Denver. “We had two goals: to prove there were people who did, and to try to learn from them about what they do to achieve this long-term weight loss.” Anyone who has lost 30 pounds and kept it off for at least a year is eligible to join the study, though the average member has lost 70 pounds and remained at that weight for six years.

Wing says that she agrees that physiological changes probably do occur that make permanent weight loss difficult, but she says the larger problem is environmental, and that people struggle to keep weight off because they are surrounded by food, inundated with food messages and constantly presented with opportunities to eat. “We live in an environment with food cues all the time,” Wing says. “We’ve taught ourselves over the years that one of the ways to reward yourself is with food. It’s hard to change the environment and the behavior.”

There is no consistent pattern to how people in the registry lost weight — some did it on Weight Watchers, others with Jenny Craig, some by cutting carbs on the Atkins diet and a very small number lost weight through surgery. But their eating and exercise habits appear to reflect what researchers find in the lab: to lose weight and keep it off, a person must eat fewer calories and exercise far more than a person who maintains the same weight naturally. Registry members exercise about an hour or more each day — the average weight-loser puts in the equivalent of a four-mile daily walk, seven days a week. They get on a scale every day in order to keep their weight within a narrow range. They eat breakfast regularly. Most watch less than half as much television as the overall population. They eat the same foods and in the same patterns consistently each day and don’t “cheat” on weekends or holidays. They also appear to eat less than most people, with estimates ranging from 50 to 300 fewer daily calories.

Kelly Brownell, director of the Rudd Center for Food Policy and Obesity at Yale University, says that while the 10,000 people tracked in the registry are a useful resource, they also represent a tiny percentage of the tens of millions of people who have tried unsuccessfully to lose weight. “All it means is that there are rare individuals who do manage to keep it off,” Brownell says. “You find these people are incredibly vigilant about maintaining their weight. Years later they are paying attention to every calorie, spending an hour a day on exercise. They never don’t think about their weight.”

Part 2 in the next post