With about one in three children in the United States obese or overweight, according to government statistics, the need for effective weight loss programs targeted to the needs of kids and their parents is clear. But, experts say, creating them will be challenging. Other than intensive hospital-based programs, few proven models exist for helping children and adolescents achieve and maintain a healthier weight. "There's a big gap" between what is available for children and what is needed, said Gary Foster, director of Temple's Center for Obesity Research and Education.