A focus on body weight may be necessary when a seriously overweight child's well-being is at stake. But parents need to be respectful and supportive, since pressuring kids—especially teens—to lose weight could cause them to overeat more or develop an eating disorder. After seeing her 18-year-old son, Wes, shave 65 pounds off his 270-pound frame, registered dietitian Anne Fletcher set out to discover the secret of other teens' success. In her recent book Weight Loss Confidential, she studies how 104 seriously overweight preteens and teens, 41 boys and 63 girls, got to a healthier weight and stayed there for two years or longer. The kids on average lost 58 pounds each, and one quarter lost 75 pounds or more. Here's how they did it:

They took the initiative. Readiness is everything, says Fletcher, and the teens she studied decided on their own when and how they were going to lose the weight. They were motivated by wanting to improve their health, look better, feel better about themselves, and improve their performance at sports and other activities.

They got active. Exercise was by far the most popular slimming strategy, with 83 percent of the teens reporting that they upped their calorie-burning efforts to lose and then to maintain. Running, walking, and lifting weights were the most common choices. Nearly two thirds of the kids continued to exercise three to five times a week.

They got real about portions. These teens know that a proper portion of meat is the size of a deck of cards and that a cup of pasta is the size of their fist. Using smaller plates and cups helped them impose limits, as did avoiding eating directly out of a bag.

They drew on support from their parents. Never underestimate the power of a cheering section. Encouraging parents who stocked the kitchen with nutritious low-calorie fare and exercised with their kids were a key to these teens' success.

They discovered what worked best for them. Some of the teens went to nutritionists for one-on-one counseling or attended summer weight camps that emphasized the importance of a healthful lifestyle. Others created their own structure, by cutting portions or giving up certain foods like french fries or soda. Fletcher's son counted calories. "Wes had always been able to eat a huge amount of food without feeling full, so this really made him start paying attention to portion sizes," she says.

They connected. Some teens discovered the power of bonding with peers in support groups like Take Off Pounds Sensibly. One girl went to meetings with her mother, and they both lost weight together.

They gave themselves time. Some of the teens lost the weight over many months or, in some cases, years. Gradual weight loss, explains Fletcher, doesn't demand the kind of deprivation required for quick results.

They didn't use the scale as their only measure of success. Although they were certainly motivated by drops in clothing sizes, the successful losers were also encouraged by feeling less winded when they climbed a flight of stairs, by improvements in their blood pressure, and by closer relationships with friends and relatives and greater self-confidence. Most realized that they were never going to reach society's thin ideal. So they chose to appreciate their assets and aimed for good health instead.