Pedestrians walk across the street near Times Square in New York. About two-thirds of American adults are overweight or obese, putting them at an increased risk for diabetes, hypertension, heart disease, osteoarthritis, stroke, gallbladder disease, sleep apnea and respiratory problems and even some cancers. Those who are extremely obese, about 100 or more pounds over a healthy weight, could be shortening their lives by as many as 10 years.