SIX years after dropping an average of 129 pounds on the TV program “The Biggest Loser,” a new study reports, the participants were burning about 500 fewer calories a day than other people their age and size. This helps explain why they had regained 70 percent of their lost weight since the show’s finale. The diet industry reacted defensively, arguing that the participants had lost weight too fast or ate the wrong kinds of food — that diets do work, if you pick the right one.
The root of the problem is not willpower but neuroscience. Metabolic suppression is one of several powerful tools that the brain uses to keep the body within a certain weight range, called the set point. The range, which varies from person to person, is determined by genes and life experience. When dieters’ weight drops below it, they not only burn fewer calories but also produce more hunger-inducing hormones and find eating more rewarding.
This coordinated brain response is a major reason that dieters find weight loss so hard to achieve and maintain. For example, men with severe obesity have only one chance in 1,290 of reaching the normal weight range within a year; severely obese women have one chance in 677. A vast majority of those who beat the odds are likely to end up gaining the weight back over the next five years. In private, even the diet industry agrees that weight loss is rarely sustained. A report for members of the industry stated: “In 2002, 231 million Europeans attempted some form of diet. Of these only 1 percent will achieve permanent weight loss.”
The specific “Biggest Loser” diet plan is probably not to blame. A previous study found similar metabolic suppression in people who had lost weight and kept it off for up to six years. Whether weight is lost slowly or quickly has no effect on later regain. Likewise — despite endless debate about the relative value of different approaches — in head-to-head comparisons, diet plans that provide the same calories through different types of food lead to similar weight loss and regain.
WHY would dieting lead to weight gain? First, dieting is stressful. Calorie restriction produces stress hormones, which act on fat cells to increase the amount of abdominal fat. Such fat is associated with medical problems like diabetes and heart disease, regardless of overall weight.
In people, dieting also reduces the influence of the brain’s weight-regulation system by teaching us to rely on rules rather than hunger to control eating.
Studies show that long-term dieters are more likely to eat for emotional reasons or simply because food is available. When dieters who have long ignored their hunger finally exhaust their willpower, they tend to overeat for all these reasons, leading to weight gain.
If dieting doesn’t work, what should we do instead? mindful eating is recommended — paying attention to signals of hunger and fullness, without judgment, to relearn how to eat only as much as the brain’s weight-regulation system commands.
Relative to chronic dieters, people who eat when they’re hungry and stop when they’re full are less likely to become overweight, maintain more stable weights over time and spend less time thinking about food. Mindful eating also helps people with eating disorders like binge eating learn to eat normally. Depending on the individual’s set point, mindful eating may reduce weight or it may not. Either way, it’s a powerful tool to maintain weight stability, without deprivation.
Diets often do improve cholesterol, blood sugar and other health markers in the short term, but these gains may result from changes in behavior like exercising and eating more vegetables.
Exercise reduces abdominal fat and improves health, even without weight loss. This suggests that overweight people should focus more on exercising than on calorie restriction.