Body not always cooperative in weight loss efforts

Tue., June 17, 2008

Shari Roan Los Angeles Times

Give your input

» Since 1994, the National Weight Control Registry has compiled information on people who have lost weight and maintained the loss. From those records, registry directors have been able to identify factors that add up to successful weight maintenance – such as regular exercise and eating breakfast.

» But many of the data have come from white women, says co-director Rena Wing of Brown Medical School. The registry needs input from all racial and ethnic groups to see whether there are differences linked to gender, race or ethnicity.

» Anyone who has lost 30 pounds or more and maintained the loss for one year or longer can enroll in the registry.

» The minimum age for participation has been 18. But the registry has started a teen branch, for people 14 and older, to learn more about how teens may differ from adults.

» Contact the registry at www.nwcr.ws or (800) 606-6927.

In her 39 years, Claudia Hallblom has, by her own estimation, lost and regained about 1,000 pounds. Her success at losing weight was always driven by a goal, such as looking nice for her graduation or wedding. Her tactics usually included strict calorie-counting.

But success on the scales was always fleeting. Sooner or later, she would revert to her old habits and no longer feel motivated to change.

“I didn’t know how to lose weight and keep it off,” the Downey, Calif., woman says.

Most people can lose weight. But few can maintain their new weight for long. Researchers are now tackling that problem, and what they’re learning is disconcerting.

The human body, it seems, is designed to sabotage weight loss at every turn – once a body has been fatter, it wants to get back to the weight that it used to be. Physiology is cruelly changed in two ways: The body needs fewer calories to maintain itself, but its craving for food is more intense.

Making sure the pounds stay off means pitting one’s willpower against a swarm of biological processes involving the brain, hormones, metabolism and fat storage.

“There is a big shift toward understanding long-term weight maintenance,” says Paul MacLean, associate professor of medicine at the University of Colorado, Denver.

“We have a huge number of diet books and diet programs, and if you do them, you can lose weight. The big problem is keeping it off. The recent estimates are that 5 percent to 10 percent of people are successful at keeping weight off on a long-term basis.”

But before you throw up your hands and reach for the Twinkies, consider this: Scientists think that understanding the stubborn biological processes at work will lead to ways to fight back.

Exercise, it’s known, buffers the post-diet body against regaining weight, in ways that researchers are just starting to comprehend. Certain foods, scientists believe, may help stave off weight regain too. And medications now in development target some of the biochemistry thought to be linked to regaining weight.

“There are strong physiological adaptations to weight loss that promote weight regain,” MacLean says. “The good news is we know a big part of the problem and why we haven’t been successful over the past several decades.”

Human biology – for obvious adaptive reasons – is designed to protect against weight loss and potential starvation. And after a period of obesity, the body may permanently alter the way weight is regulated by more aggressively stimulating appetite and signaling the body to protect fat stores.

Metabolism has changed: the body now needs about eight fewer calories per day for each pound of weight that was lost. That means someone who loses 40 pounds will require about 320 calories fewer each day than they did before the weight loss.

This difference in energy needs before and after weight loss has been dubbed the “energy gap” by University of Colorado professor James O. Hill, director of the Center for Human Nutrition in Denver.

Appetite hormones change, too. The hormone leptin, for example, is a major appetite regulator – it tells the body to stop eating and store fat after meals.

Some people may be genetically prone to having lower leptin levels, making them more prone to obesity. But studies also show that, after a weight loss, leptin levels are lower than what they used to be. That means appetite is less easily quelled.

Another hormone, ghrelin, stimulates food intake – levels in the brain fall lower after a meal. However, after a weight loss, ghrelin levels in the blood generally increase, and the fall-off after mealtimes isn’t as marked.

“You lose 10 percent of your body weight. All of a sudden all these systems kick in to try to keep you from losing weight,” says Dr. Ken Fujioka, director of nutrition and metabolic research at the Scripps Clinic in San Diego.

“People are mad at themselves or depressed after they regain the weight. But I explain: It’s not you. Biology has kicked in now. … You are hungry all the time. You think about food all the time.”

The weight comes back fast.

“The entire system is saying, ‘Bring the calories in, store them efficiently and do not reduce these signals until the fat is returned that was there before,’ ” MacLean says. “You may look like a lean person, but your body hasn’t changed inside.”

Moreover, animal studies show that most of the regained weight is distributed as visceral fat – the abdominal paunch that is linked to heart disease and diabetes.

So what is a dieter to do?

“There is nothing we know of that does anything to reverse this,” Fujioka says of the biological forces that defend body fat. “It’s very tough.”

But it’s not impossible. The National Weight Control Registry is an honor roll of dieters who have fought and won. Started in 1994 by Hill and Rena Wing, director of the weight control and diabetes research center at Brown Medical School, the registry provides data on how regular people have managed to keep weight off.

Based on data from more than 7,000 people, Wing says there are few similarities in how people lose weight. But those who succeed in maintenance sing the same song.

Instead of trying to eat less for the rest of their lives to bridge the energy gap, these people exercise more.

Physical activity, in ways that researchers don’t really understand, influences some of the biological systems that promote weight regain, encouraging the body to become more sensitive to leptin and insulin, for example.

“Everyone thinks exercise is about burning calories,” Fujioka says. “But you are actually returning the system to more like what it should be. Things start working again.”

The successful maintainers also change what they eat: The registry found that they keep their calories in careful balance with what they expend – religiously referring to calorie charts and writing down everything they consume. They also tend to eat low-fat foods.

But there may be more nuances to food choices than that.

“We’re getting more interested in studies that look at food composition,” Fujioka says. “It could be that eating certain nutrients may also help the system work better.”

Scientists don’t know how long it would take to return the physiological responses of a once-obese body to normal – or if, indeed, that ever is quite possible.

Studies do show, however, that weight regain is most likely in the first couple of years after weight loss.

“After that, it’s as if you master the technique,” Wing says.

The current research on obesity strongly points to two messages that rely heavily on human behavior: Don’t gain excess weight in the first place, and if you do, be prepared to make permanent lifestyle changes to lose it and maintain the loss.