WEIGHT-LOSS REDUCES ABDOMINAL FAT AND IMPROVES INSULIN ACTION IN MIDDLE-AGED AND OLDER MEN WITH IMPAIRED GLUCOSE-TOLERANCE

Aging is associated with an increased accumulation of abdominal fat, g lucose intolerance, and insulin resistance. We tested the hypothesis t hat diet-induced weight loss would reduce the abdominal distribution o f fat and improve glucose tolerance and insulin action in a group of o bese middle-aged and older men with normal or impaired glucose toleran ce (IGT). Oral glucose tolerance tests (OGITs) were performed at basel ine and after 9 months of diet-induced weight loss in 35 men (mean age , 60 +/- 8 years). Fifteen men of comparable age and degree of obesity who did not participate in the weight loss intervention served as con trols. Subjects lost 9.0 +/- 2.0 kg (mean +/- SD) body weight (P <.001 ), resulting in a 19% reduction in percent body fat (30.0 +/- 4.0% to 24.0% +/- 4.0%, P <.001), an 8% reduction in waist circumference (104. 0 +/- 7.0 to 96.0 +/- 7.0 cm, P <.001), and a 2% reduction in waist to hip ratio [WHR] (0.97 +/- 0.06 to 0.95 +/- 0.06, P <.01). Weight loss improved glucose tolerance: nine men with IGT at baseline reverted to normal glucose tolerance following the intervention. Glucose area dur ing the OGTT was significantly reduced after weight loss (-22.0%, P <. 001), while it increased in control subjects (+32%, P <.004). In multi ple regression analysis, the improvement in glucose area following wei ght loss in these 35 men was attributed to the reduction in waist circ umference (P <.01) and baseline glucose area (P <.05). Insulin respons e to glucose and tissue sensitivity to endogenous insulin were measure d in a subset of eight men using the hyperglycemic clamp technique. We ight loss resulted in significant reductions in acute (P <.05) and sec ond-phase (P <.01) insulin responses and a significant increase in the rate of glucose utilization {[M] P <.05), indicative of increased tis sue sensitivity to insulin. Our results support the hypothesis that we ight loss significantly improves glucose tolerance and insulin action in obese middle-aged and older men with normal glucose tolerance or IG T, in part by reducing the distribution of fat in upper-body sites. Co pyright (C) 1995 by W.B. Saunders Company.