"More than 30 percent of children and adolescents in the Americas - are overweight or obese," said lead reviewer Hiltje Oude Luttikhuis, of the Beatrix Children's Hospital in Groningen, the Netherlands. "Even in the Netherlands, this prevalence in childhood obesity is going up. We conducted this study because we wanted to understand how best to intervene."The work appeared in The Cochrane Library, a publication of the Cochrane Collaboration, an international nonprofit that evaluates medical research. The review found that the most encouraging studies pointed up the importance of using a combination of diet, physical activity and behavior change to reduce weight - all coupled with a generous portion of parental involvement. All together, the 64 studies included 5,230 subjects. Fifty-four of the studies, encompassing 3,806 participants, focused on changing some aspect of lifestyle, especially in the areas of diet, physical activity or other behaviors. The other 10 studies, with 1,424 participants, focused on using drugs, in addition to lifestyle changes. Researchers used the drugs orlistat and sibutramine on moderately to severely obese teens. Orlistat is taken with meals and inhibits the absorption of fats. Sibutramine suppresses appetite, making the subject feel full. Because of the drugs' side effects, Oude Luttikhuis said, drug therapy should be used, if it's used at all, in combination with lifestyle interventions.