Smartphones have the capability to monitor health-related behaviors (exercise, diet, etc.) and provide social support which has the potential to play a powerful role in health promotion. The objective of this study is to refine and pilot test the Social POD app for personalized health monitoring and interaction founded on a combination of social networks, recommender systems, motivational research, and health behavior theory. The aim of our proposed project is to conduct a 3-month pilot RCT among overweight and obese adults (N=150) comparing a theory-based podcast (TBP) plus self-monitoring using a commercially-available calorie and weight tracking app (current most popular diet self-monitoring method) versus TBP plus self-monitoring and social support/incentive points for participating with the Social POD app (TBP+Social POD).