Minor long‐term changes in weight have beneficial effects on insulin sensitivity and β‐cell function in obese subjects

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Abstract
SUMMARY Aim To evaluate the long‐term effect of changes in body composition induced by weight loss on insulin sensitivity (SI), non‐insulin mediated glucose disposal, glucose effectiveness (SG) and β‐cell function. Design Glucose metabolism was evaluated before and after participation in a two‐year weight loss trial of Orlistat vs. placebo, combined with an energy and fat restricted diet. Subjects Twelve obese patients (11 women, 1 man), age 45.8 ± 10.5 years, body weight (BW) 99.7 ± 13.3 kg, BMI 35.3 ± 2.8 kg/m2. Measurements At inclusion and 2 years later an oral glucose tolerance test (OGTT) and a frequently sampled intravenous glucose tolerance test (FSIGT) were performed. Body composition was estimated by a dual‐energy X‐ray absorptiometry (DXA) whole body scanning. Results The patients obtained varying changes in BW ranging from a weight loss of 17.8 kg to a weight gain of 6.0 kg. Corresponding changes in fat mass (FM) varied from a 40% reduction to a 19% increase. A significant decrease in both fasting (p = 0.038) and 2 h (p = 0.047) blood glucose at OGTT was found. The improvement in insulin sensitivity (SI) estimated by means of Bergmans Minimal Model, was significantly and linearly correlated to change in total FM (r = − 0.83, p = 0.0026). A multiple regression analysis showed that changes in truncal FM was the strongest predictor of change in SI explaining 67% of the variation. First phase insulin response (AIRg) remained unchanged whereas insulin disposition index increased significantly (p = 0.044). At inclusion five patients had impaired glucose tolerance of which four, who lost weight, were normalized at the retest 2 years later. Conclusion In obese subjects long‐term minimal or moderate changes in weight were found to be linearly associated with changes in insulin sensitivity. In obese subjects with impaired glucose tolerance even a minor weight loss was able to normalize glucose tolerance.