Effects of weight loss on norepinephrine and insulin levels in obese older men

Abstract

Older individuals have higher plasma insulin and norepinephrine (NE) levels than the young. This may be due to biological aging; however, these changes also may be due in part to the increase in abdominal obesity that often accompanies aging. The latter possibility was tested by examining the effects of weight loss on plasma insulin and NE levels in 11 healthy men aged 52 to 72 years who had mild to moderate obesity (body mass index [BMI], 27 to 36 kg/m 2). Plasma insulin levels were measured during an oral glucose tolerance test, and on a second day NE levels were measured during supine rest and upright posture. Subjects lost 10 ± 5 kg (mean ± SD) and decreased their waist to hip ratio ([WHR] an index of the pattern of regional fat distribution) 2.8% ( P < .01) over 9 ± 3 months through mild caloric restriction. This resulted in a 23% decrease ( P < .05) in fasting insulin levels and a 48% decrease ( P < .01) in 2-hour insulin levels. Weight loss also resulted in a 31% decrease ( P < .001) in supine plasma NE levels and an 8% decrease ( P < .05) in supine diastolic blood pressure (BP). Decreases in supine plasma NE levels correlated with changes in WHR ( r = .61, P < .05), but did not correlate with changes in other measures of body composition or with changes in glucose and insulin levels. These results suggest that higher plasma NE levels are related to the distribution of body fat to upper-body or abdominal sites in obese older men.