For the first time in human history, the numbers of overweight and underweight individuals are about the same, at 2.1 billion each. Along with the current worldwide obesity epidemic is the explosion of obesity- and overweight-related health problems, including diabetes and the metabolic syndrome, musculoskeletal disorders,cardiovascular disease, pulmonary disorders, and certain forms of cancer. Obesity and overweight account for a significant percentage of overall health care costs and contribute significantly to morbidity and mortality in the United States and around the world.