No effect of short-term dietary supplementation of saturated and poly- and monounsaturated fatty acids on insulin secretion and sensitivity in healthy men.

To evaluate the short-term influence of fatty acids with different grades of saturation on insulin secretion and sensitivity, 8 healthy males (age 26 +/- 3.5 years, body mass index 22.4 +/- 1.8 kg/m2) were provided with 800 kcal daily of either carbohydrates (CH; 200 g), or fat (90 g) enriched either with saturated fatty acids (SAFA; 72%) or (omega-6) polyunsaturated fatty acids (PUFA; 60%) or cis-monounsaturated fatty acids (MUFA; 40%; n = 5) in addition to a standard diet (2,000 kcal/ day; 50% CH, 15% protein, and 35% fat; 33% SAFA, MUFA, and PUFA each) for 1 week in a randomized order (washout period 2 weeks). The stimulated insulin secretion was quantified by the frequently sampled intravenous glucose tolerance test (FSIGT; 0.3 g glucose/kg body weight), while the insulin sensitivity was determined by an euglycemic-hyperinsulinemic 5-mU clamp. In parallel, basal and stimulated carbohydrate and fat oxidation rates were estimated by indirect calorimetry. One week of defined fat exposure failed to significantly affect the glucose-induced insulin secretion during FSIGT and insulin-dependent glucose disposal during an euglycemic clamp (M values: CH 9.6 +/- 1.6 mg/kg.min, SAFA 9.7 +/- 2.2, PUFA 9.8 +/- 2.5, and MUFA 11.5 +/- 3.2 mg/kg.min; NS). In addition, oxidation rates for fat and glucose in the postabsorptive state and during hyperinsulinemia did not differ between the different diets. We conclude that short-term (1-week) isocaloric supplementation of a standard diet with fatty acids of varying degree of saturation does not affect either insulin secretion or insulin sensitivity in healthy men, due to the compensatory metabolic capacity of healthy subjects.