Many states wish to improve healthy lifestyles. Weight (kg) / height (m)^2 (weight (lb) / height (inch)^2) x703. Often correlates with degree of body fatness and disease risk. Used to evaluate health risk associated with underweight or overweight. Bmi values not very useful for evaluating non-obese people"s fatness. How much of a person"s weight is fat. Athletes, pregnant and lactating women, adults over age 65. Reflects the degree to visceral fatness in proportion to body fatness. Central obesity: large deposits of visceral fat, causing beer belly . Risk of diabetes, stroke, hypertension, coronary artery disease. Over-fat greater than 32%, 35% if over 40. Underweight people should gain body fat as an energy reserve and to acquire reserves of nutrients. Change in energy stores = energy in energy out. How many calories do i need each day. Basal metabolism: sum total of energy expended on all of the involuntary activities needed to sustain life.