Self-management is critical for the prevention and control of chronic health conditions. Research shows that dietary and physical activity behaviors related to obesity are inextricably linked to the development, course, and outcomes of Type 2 diabetes and its comorbidities. Therefore, a compelling case has been made for behavioral lifestyle intervention as the first-line approach. Academic psychologists and other behavioral scientists have contributed to all stages of obesity and diabetes prevention research and practice. They have made seminal contributions to the evidence-based science of health behavior change with the National Institutes of Health funded Diabetes Prevention Program randomized clinical trial and subsequent translation and dissemination efforts as exemplars. Beginning with social–cognitive learning theory and behavior modification for obesity, research psychologists have elucidated the critical elements associated with treatment efficacy and have demonstrated the benefits of identifying individuals at elevated risk and providing early intervention. Most often, the psychologist’s role has been to design and evaluate programs based on behavioral principles, or supervise, train, and facilitate adherence to interventions, rather than function as the primary provider. Lifestyle interventions have made a strong public health impact, but pressing challenges remain. Issues include difficulties with long-term weight loss maintenance, heterogeneity of treatment response, pragmatic translation and dissemination concerns such as optimal training and delivery formats, scalability of lifestyle intervention programs, reimbursement, and a need for environmental and policy approaches that promote healthy lifestyle norms and behaviors for all communities. Health psychology should be at the forefront in addressing all of these concerns.