Cellular, metabolic, and clinical consequences of adipose mass enlargement in obesity.

When adipose tissue enlarges in obesity, as the result of an imbalance between caloric intake and caloric expenditure, many changes occur in the cellular components of the adipose mass. A combination of increased cell size and number underlies the accretion of the adipose mass, however, only a reduction in cell size is possible with weight loss. Several metabolic abnormalities accompany obesity--most important--hyperinsulinemia, hyperlipidemia, insulin resistance, and carbohydrate intolerance. Clinical consequences of obesity include hypertension, venous insufficiency, gallbladder disease, osteoarthritis, pulmonary and cardiovascular insufficiency, diabetes, and atherosclerotic cardiovascular disease, and all are dependent on the severity and duration of the obesity. Once established, obesity is difficult to correct because of the development of many adaptive mechanisms by which obesity defends itself.