Book excerpt: The primary purpose of fitness and body composition standards in the U.S. Armed Forces has always been to select individuals best suited to the physical demands of military service, based on the assumption that proper body weight and composition supports good health, physical fitness, and appropriate military appearance. The current epidemic of overweight and obesity in the United States affects the military services. The pool of available recruits is reduced because of failure to meet body composition standards for entry into the services and a high percentage of individuals exceeding military weight-for-height standards at the time of entry into the service leave the military before completing their term of enlistment. To aid in developing strategies for prevention and remediation of overweight in military personnel, the U.S. Army Medical Research and Materiel Command requested the Committee on Military Nutrition Research to review the scientific evidence for: factors that influence body weight, optimal components of a weight loss and weight maintenance program, and the role of gender, age, and ethnicity in weight management.