Family physicians are often asked for advice by patients of all ages who participate in regular exercise programs. The knowledgeable family physician can be very helpful to athletes, who are swamped with information and misinformation about nutrition. This article describes the dietary needs of recreational and competitive athletes, illustrates the way in which diet can prevent the development of some pathological conditions, considers athletes at different stages of the life cycle, and discusses the dietary requirements of the exercising diabetic patient.