Lewis Kuller will discuss how obesity is an example of a common source epidemic due to changes or introduction of new behaviors, i.e. lifestyles, which result in introduction of new "agents," such as fast foods or calorically dense foods, into a receptive environment. The development of technology for mass production of low-cost, high-calorically dense foods has resulted in economic advantage, mass marketing, and social acceptability. Over time, this has caused increased risks of obesity, diabetes, cardiovascular disease, and cancer, etc. Successful control of the obesity epidemic requires an understanding of the interrelationship between the host, the agents and the environmental factors.