Studies show that virtually all increases in children's (5-12yrs) BMI occur during the summer, no matter children's' weight status (i.e., normal weight, overweight, or obese) at summer entry. Recent preliminary studies show that children engage in healthier behaviors on days that they attend summer day camps, and that BMI gain does not accelerate for these children. The proposed randomized dose-response study will identify the dose-response relationship between amount of summer programming and summer BMI gain.