Obesity is a particularly vexing public health challenge, since it not only underlies much disease and health spending but also largely stems from repeated personal behavioral choices. The newly enacted comprehensive health reform law contains a number of provisions to address obesity. For example, insurance companies are required to provide coverage for preventive-health services, which include obesity screening and nutritional counseling. In addition, employers will soon be able to offer premium discounts to workers who participate in wellness programs that emphasize behavioral choices. These policies presume that government intervention to reduce obesity is necessary and justified. Some people, however, argue that individuals have a compelling interest to pursue their own health and happiness as they see fit, and therefore any government intervention in these areas is an unwarranted intrusion into privacy and one's freedom to eat, drink, and exercise as much or as little as one wants. This paper clarifies the overlapping individual, employer, and social interest in each person's health generally to avoid obesity and its myriad costs in particular. The paper also explores recent evidence on the impact of government interventions on obesity through case studies on food labeling and employer-based anti-obesity interventions. Our analysis suggests a positive role for government intervention to reduce and prevent obesity. At the same time, we discuss criteria that can be used to draw lines between government, employer, and individual responsibility for health, and to derive principles that should guide and limit government interventions on obesity as health reform's various elements (e.g., exchanges, insurance market reforms) are implemented in the coming years.