Physiological and metabolic consequences of obesity.

Fasting plasma insulin levels provide an indirect indication of insulin resistance. Glucose utilization rate, measured by the euglycemic clamp technique, is a direct measure of insulin sensitivity. Insulin sensitivity decreases with increasing body mass index (BMI) in the range of 27 to 35 kg/m2. A higher waist-to-hip ratio is associated with lower insulin sensitivity, after adjusting for BMI. Obese patients have higher plasma free fatty acid levels and less suppression of lipolysis by insulin than lean individuals. The increased supply of fatty substrates and their competition with glucose for oxidation constitute a component of insulin resistance in obesity. Both systolic and diastolic blood pressure are increased with BMI. The hemodynamic effects may be due to an increase in cardiac output and enhanced activity of the adrenergic nervous system.