Poor diet and physical inactivity account for 400,000 deaths a year and may soon overtake tobacco as the leading cause of mortality in the United States. Effective interventions are needed to modify diet and exercise and to maintain these behaviors over time. The worksite is an ideal setting for interventions to promote nutrition and physical activity because both the individual and the environment can be targeted. Dr. Thorndike's career goal is to become an independent clinical investigator in behavioral interventions for lifestyle modification to prevent obesity and chronic disease. Building on her previous experience in tobacco control research, her proposal outlines a plan for transitioning her career focus to developing behavioral interventions to modify diet and exercise. Aided by intensive coursework in health behavior interventions, exercise physiology, and cost-effectiveness analysis, Dr. Thorndike proposes to assess the Massachusetts General Hospital's employee wellness program (Be Fit) and to conduct a randomized trial of an innovative Internet-based maintenance program. She uses the RE-AIM model for evaluating health promotion programs to assess the reach, effectiveness, adoption, and maintenance of the interventions. The results of this research will help inform the design of future interventions. The Specific Aims of the research are: Specific Aim 1: To determine the effectiveness of a 12 week intensive employee wellness program (Be Fit). Specific Aim 2: To complete a randomized controlled trial to assess whether a 9-month Internet-based self- monitoring maintenance program following the intensive Be Fit program increases the likelihood that participants will maintain the behavioral and health benefits achieved during the 12 week program. Specific Aim 3: To assess the reach and adoption of the Be Fit wellness program. Specific Aim 4: To perform a societal-perspective cost-effectiveness analysis of the Internet-based maintenance program. This career development award will allow Dr. Thorndike to acquire additional research skills and experience under the mentorship of nationally recognized researchers in a supportive academic environment and will allow her to achieve her goal of becoming an independent patient-oriented researcher in lifestyle modification interventions to prevent obesity and chronic disease. RELEVANCE (See instructions): Building on the candidate's previous experience in tobacco control research, the award will allow the candidate to become an independent investigator in patient-oriented research focused on lifestyle modification to prevent obesity and chronic disease. The research project addresses obesity prevention at both the individual and the environmental level with an intervention to initiate and maintain changes in diet and fixfirr.isfi for fimnlnvfifis at a large urban worksite..