Pathophysiology of obesity.

Individuals weighing greater than 100 kg represent a small fraction of the population and yet pose a major health risk to themselves. It is proposed that individuals be classified according to their body mass index (BMI). Class 0 individuals have a BMI of 20-25 kg/m2 and are not obese; Class I individuals have a BMI of 25-30 kg/m2 and are at low risk from their obesity; Class II individuals have a BMI of 30-35 kg/m2 and have moderate risk; Class III individuals have a BMI of 35-40 kg/m2 and have high risk associated with their obesity; Class IV individuals have a BMI of greater than 40 kg/m2 and are at very high risk for illness. Class IV is the primary group for surgical consideration. The pathophysiologic consequences of excess weight result in large part from increased food intake and/or decreased physical activity. Individuals in Class IV have additional problems related to their weight, including cardiomyopathy, Pickwickian/sleep apnea syndrome, pituitary/gonadal dysfunction, acanthosis nigricans, and significant osteoarthritis.