This is the VOA Special English Health Report.

A listener has written from China for advice about how to lose weight. Michael in Shanghai says he is twenty-six years old and has battled obesity for most of his life.

Doctors say obesity, also known as severe overweight, is a complex condition. A doctor may advise medical interventions in addition to changes in behavior. But experts say the most successful weight-loss plans include a well-balanced diet and exercise.

People who want to avoid weight gain have to balance the number of calories they eat with the number of calories they use. To lose weight, you can reduce the number of calories you take in, or increase the number you use, or both.

Experts at the National Institutes of Health say to lose weight, a person should do an hour of moderate to intensive physical activity most days of the week. This could include fast walking, sports or strength training.

You should also follow a nutritious eating plan and take in fewer calories than your body uses each day.

A recent study looked at four of the most popular dieting plans in the United States. Researchers at Stanford University in California studied more than three hundred overweight women, mostly in their thirties and forties.

Each woman went on one of the four plans: Atkins, The Zone, Ornish or LEARN. The women attended diet classes and received written information about the food plans.

At the end of a year, the women on the Atkins diet had lost the most, more than four and one-half kilograms on average. They also did better on tests including cholesterol levels and blood pressure. 

Christopher Gardner led the study, reported in the Journal of the American Medical Association. He says the Atkins diet may be more successful because of its simple message to lower intake of sugars. Also, he says the advice to increase protein in the diet leads to more satisfying meals.

He says there was not enough money to also study men, but that men would probably have similar results.

But last week, another report suggested that only a small minority of people have long-term success with dieting. The report in the journal American Psychologist was based on thirty-one studies.

Researchers at the University of California, Los Angeles, medical school found that most dieters regained their lost weight within five years. And often they gained back even more. But those who kept the weight off generally were the ones who exercised.

And that's the VOA Special English Health Report, written by Caty Weaver. I’m Katherine Cole.