POTENTIATION OF EFFECTS OF WEIGHT-LOSS BY MONOUNSATURATED FATTY-ACIDSIN OBESE NIDDM PATIENTS

Although moderate weight loss improves glycemic control in obese NIDDM patients, quite often it is not normalized. To determine whether the response to weight loss can be improved by altering the macronutrient composition of hypocaloric diets, 17 obese NIDDM patients were studied at 1) baseline, 2) after dieting for 6 weeks on a formula diet enrich ed in either monounsaturated fatty acids (MUFAs, n = 9) or carbohydrat es (CHOs, n = 8) at a 50% caloric deficit, and 3) after 4 weeks of pos tdiet refeeding on the respective formulas with caloric intake titrate d to achieve weight maintenance. Fasting, 24-h, and oral glucose toler ance test (OGTT) blood glucose, plasma insulin, and C-peptide levels w ere measured. All prediet parameters were similar between groups. Afte r dieting, although weight loss was similar between groups, the fastin g glucose level decreased significantly more in the MUFA group (-4.6 /- 0.7 mmol/l) than in the CHO group (-2.4 +/- 1.0 mmol/l; P < 0.05). Twenty-four-hour glycemia decreased in both groups after dieting, but the MUFA group had a greater decrease than the CHO group (P < 0.05, an alysis of variance [ANOVA]). Although decreases in fasting glycemia we re maintained in both groups after refeeding, postprandial glycemia de teriorated after refeeding with 1 the CHO- but not the MUFA-enriched f ormula (P < 0.05). After dieting and refeeding, fasting C-peptide incr eased 204 +/- 47 pmol/l in the MUFA group, but the CHO group remained at prediet levels (P < 0.05). Twenty-four-hour C-peptide levels were s imilar between groups after dieting and refeeding, despite the lower g lycemia and CHO content of the MUFA formula. However, when equal amoun ts of CHO were consumed during the OGTT, the MUFA group had significan tly higher C-peptide levels after both dieting and refeeding (P < 0.05 ). Fasting, 24-h, and OGTT insulin levels were similar between groups throughout the study. These results indicate that macronutrient compos ition is an important determinant of the glycemic response to weight-l oss therapy in obese NIDDM patients. Based on the C-peptide response d uring the OGTT, increased CHO-induced insulin secretion is one possibl e mechanism by which this occurs.