Prevention is key for combating obesity, but few programs have prevented future increases in body mass index (BMI) and onset of overweight/obesity, particularly during late adolescence when youth often assume responsibility for dietary intake and exercise choices. One exception is a brief 6-hr dissonance-based group program (Project Health)wherein participants make small lasting incremental lifestyle changes to dietary intake and exercise to reach energy balance. Group participants discuss costs of obesity, an unhealthy diet, and sedentary behavior, and benefits of leanness, a healthy diet, and exercise. These discussions prompt them to align their attitudes with their publically displayed behavior.