Differences in insulin resistance do not predict weight loss in response to hypocaloric diets in healthy obese women.

The current study was initiated to determine whether insulin resistance and/or hyperinsulinemia affected the ability of obese individuals to lose weight in response to hypocaloric diets. Thirty-one obese, nondiabetic women, with values for body mass index ranging from 28.0-35.0 kg/m2, volunteered for this program. Resistance to insulin-mediated glucose disposal was assessed by determining their steady state plasma insulin and glucose concentration during the last 30 min of a 180-min infusion of somatostatin, insulin, and glucose. The total integrated insulin response to breakfast and lunch was also determined. After the baseline measurements, volunteers were placed on a hypocaloric diet calculated to lead to a minimum weekly loss of 1% of ideal body weight. Individuals who met the criteria after 30 days of dieting were defined as weight loss successes (n = 20) and continued on the diet for another 30 days. Individuals not meeting the criteria were designated as weight loss failures (n = 12) and were discharged from the study. There was a mean (+/-SEM) weight loss at 60 days of 9.2 +/- 0.4 kg in the 20 individuals defined as weight loss successes, but there was no correlation between weight loss and either steady state plasma glucose or the total integrated insulin response (r < 0.1; P > 0.83). Furthermore, using the same criteria to define insulin sensitivity and insulin resistance as those for therapeutic successes, the therapeutic failures comprised six insulin-sensitive and five insulin-resistant subjects. In summary, insulin-mediated glucose disposal varied widely in nondiabetic, obese women, and there was no relationship between baseline insulin resistance or total integrated insulin response and weight loss. It is concluded that the ability to lose weight on a calorie-restricted diet over a short time period does not vary in obese, healthy women as a function of insulin resistance or hyperinsulinemia.