Nutritional Effects on Measurement of Insulin Sensitivity

Partial replacement of carbohydrates with unsaturated fat may improve insulin sensitivity in a population at risk for cardiovascular disease….

Results from the OmniHeart Trial suggest an alternative approach to improving insulin sensitivity by modifying the macronutrient composition.

This study was a randomized, controlled, three-period, crossover feeding study that included 164 individuals above the age of 30 with prehypertension or stage 1 hypertension without diabetes. Exclusion criteria included pre-existing diabetes; active or prior CVD, LDL cholesterol >220mg/dL; fasting triglycerides >750mg/dL, weight >350lbs; use of insulin, hypoglycemic agents, medications that affect blood pressure or lipids, use of vitamin or mineral supplements, and self-reported alcohol intake of >14 drinks per week.

Three separate diets were examined to determine their effects on insulin sensitivity, including a carbohydrate rich diet (CARB- which is similar to the Dietary Approaches to Stop Hypertension diet), a protein-rich diet (PROT- protein was predominantly from plant sources), and an unsaturated fat-rich diet (UNSAT- mostly monounsaturated fats). Each diet was administered for 6 weeks, followed by a washout period of 2-4 weeks. Weight was held constant throughout the course of the study.

The primary outcome was the quantitative insulin sensitivity check index (QUICKI) using the end-of-period fasting serum glucose and insulin. At baseline, mean QUICKI was 0.35. The UNSAT diet increased QUICKI by 0.007, the CARB diet increased the QUICKI by 0.002, and the PROT diet increased the QUICKI by 0.004. Similar diet responses were found using 1/HOMA.

Overall, statistically significant improvements in insulin sensitivity were demonstrated following administration of the UNSAT diet.

The UNSAT diet consists of 37% kcals from unsaturated fat, which is similar to that of Mediterranean-style diets. Authors of the OmniHeart trial suggest that Mediterranean-style dieting may offer an alternative to weight loss when trying to improve insulin sensitivity.

https://care.diabetesjournals.org/content/36/5/1132.full.pdf+html doi: 10.2337/dc12-0869; Diabetes Care May 2013 vol. 36 no. 5 1132-1137