Effect of caloric restriction with or without n-3 polyunsaturated fatty acids on insulin sensitivity in obese subjects: A randomized placebo controlled trial

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BackgroundCaloric restriction and n-3 polyunsaturated fatty acid (PUFA) supplementation protect from some of the metabolic complications. The aim of this study was to assess the influence of a low calorie diet with or without n-3 PUFA supplementation on glucose dependent insulinotropic polypeptide (GIP) output and insulin sensitivity markers in obese subjects. MethodsObese, non-diabetic subjects (BMI 30–40kg/m2) and aged 25–65yr. were put on low calorie diet (1200–1500kcal/day) supplemented with either 1.8g/day n-3 PUFA (DHA/EPA, 5:1) (n=24) or placebo capsules (n=24) for three months in a randomized placebo controlled trial. Insulin resistance markers and GIP levels were analysed from samples obtained at fasting and during an oral glucose tolerance test (OGTT). ResultsCaloric restriction with n-3 PUFA led to a decrease of insulin resistance index (HOMA-IR) and a significant reduction of insulin output as well as decreased GIP secretion during the OGTT. These effects were not seen with caloric restriction alone. Changes in GIP output were inversely associated with changes in red blood cell EPA content whereas fasting GIP level positively correlated with HOMA-IR index. Blood triglyceride level was lowered by caloric restriction with a greater effect when n-3 PUFA were included and correlated positively with fasting GIP level. ConclusionsThree months of caloric restriction with DHA+EPA supplementation exerts beneficial effects on insulin resistance, GIP and triglycerides. General significanceCombining caloric restriction and n-3 PUFA improves insulin sensitivity, which may be related to a decrease of GIP levels.