The U.S. Preventive Services Task Force has recommended that primary care clinicians screen all adults for obesity and provide those affected intensive multicomponent behavioral interventions. Approximately 95 million U.S. adults qualify for such care, also referred to as lifestyle modification. Using the Guidelines (2013) for Managing Overweight and Obesity in Adults (hereafter, Obesity Guidelines) as a framework, this article reviews the principal components of comprehensive lifestyle modification, which include diet, physical activity, and behavior therapy. To lose weight, the Obesity Guidelines recommend participation for 6 months in high-intensity programs that provide 14 or more counseling sessions with a trained interventionist. When provided face-to-face individual or group treatment, participants lose up to 8 kg (8% of weight) in 6 months and experience improvements in cardiovascular disease risk factors and quality of life. To prevent weight regain, the Obesity Guidelines recommend participation for 1 year in weight-loss-maintenance programs that provide at least monthly counseling. High levels of physical activity, frequent monitoring of body weight, and consumption of a reduced-calorie diet are associated with long-term weight loss. Investigators currently are seeking to increase the availability of lifestyle modification by delivering it in community-based programs, as well as on digital platforms (e.g., Internet and Smartphone). Digitally delivered programs lower costs and expand treatment reach; their efficacy is likely to improve further with the addition of new technologies for monitoring food intake, activity, and weight. Ultimately, to improve long-term weight management, individual lifestyle counseling must be joined with collective and institutional efforts to improve the nation's eating and activity environments. (PsycINFO Database Record (c) 2020 APA, all rights reserved).