Losing weight may be easy; it’s keeping it off that is difficult. Scientists now have a better understanding of long-term weight maintenance:
In her 39 years, Claudia Hallblom has, by her own estimation, lost and regained nearly 455 kilograms.
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 her success 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, California, woman says.
Most people can lose weight. But few can maintain it. Researchers are now tackling that problem, and what they’re learning is disconcerting. The human body is designed to sabotage weight loss at every turn — once a body has been fatter, it wants to revert to what 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.
Keeping the pounds at bay means pitting one’s willpower against several 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. “You can easily lose weight; the big problem is keeping it off.”
However, scientists think that understanding the stubborn biological processes at work will lead to ways to fight back.
Exercise buffers the post-diet body against regaining weight, in ways that researchers are just starting to comprehend. Certain foods 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.
Human biology is designed to protect against weight loss and potential starvation. After a period of obesity, the body may permanently alter the way weight is regulated by more aggressively stimulating appetite and signalling 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 is lost. This difference in energy needs before and after weight loss has been dubbed the “energy gap”.
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. Its levels in the brain fall after a meal. However, after a weight loss, ghrelin levels generally increase, and the fall after mealtimes isn’t as marked.
“You lose 10 per cent 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… You are hungry all the time.”
And the weight comes back fast. “You may look like a lean person, but your body hasn’t changed inside,” says MacLean.
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,” says Fujioka.
But it’s not impossible. Based on data from more than 7,000 people, Rena Wing, director of the weight control and diabetes research centre at Brown Medical School, 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 influences some of the biological systems that promote weight regain, encouraging the body to become more sensitive to leptin and insulin, for example.
The successful maintainers also change what they eat: the registry found that they keep their calories in careful balance with what they expend. 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 strongly points to two messages: 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.
Sources: The Telegraph (Kolkata, India)