The Amercian Medical Association is out with a determination that labels obesity as a disease. Dr. Bruce Nash is the chief medical officer for C.D.P.H.P. Diet, exercise, and heredity, could all be factors. Doctors use what they call the body mass index or the B.M.I. as a tool to measure potential problems. The index is the measure of body fat based on height and weight. Nash says a number of 25 or below is ideal.