For the first time, scientists may be able to explain dieters' complaints that no matter how hard they try, they can't keep off lost weight.
Researchers at the New York Obesity Research Center at Rockefeller University report today on 10 years of painstaking research that shows that the body goes to remarkable lengths to maintain the weight you started your diet with.
It does so by slowing metabolism -- reducing the number of calories required for breathing, maintaining body temperature, circulating blood and even digesting food -- while increasing the efficiency of muscles so that fewer calories are burned during exercise.
The results, which appear in the New England Journal of Medicine, were obtained in special hospital laboratories where the researchers could measure every calorie consumed by subjects and every calorie spent.
The findings indicate that the individual who loses weight faces a lifelong battle to maintain that loss.
"You can't simply go on a diet and eradicate the [obesity] problem," said Dr. Jules Hirsch of Rockefeller. "People who lose weight are going to continue to have this underlying problem" that will lead to a regaining of the weight unless they eat less, increase their physical activity or both, he said.
The study suggests that a dieter who does not exercise will have to consume 15 percent fewer calories than researchers had previously believed in order to maintain the reduced weight. Those who do exercise can eat a little more.
The new results and other studies also should help to change the attitude of physicians, employers and others who castigate the obese for their overeating and lack of willpower, Dr. William I. Bennett of the Cambridge Hospital wrote in an accompanying editorial.
Dieters, he said, "will not be helped by relentless moralizing and easy solutions reflecting a theory of gluttony that does not stand up to the available evidence."
Obesity is a major health problem in the United States, and one that continues to grow. Today, one in every three people in this country is overweight, compared with one in every four in 1980.
The 18 obese volunteers and 23 of normal weight who participated in the Rockefeller study were hospitalized for periods ranging from weeks to months.
