Increased fiber intake predicts the decrease in 2nd phase glucose-induced hyperinsulinemia following a hypocaloric diet in obese subjects

Abstract Background and Aims Higher fiber intake is associated with increased insulin sensitivity (IS) and reduced glucose-induced insulin secretion (GIIS) during isocaloric-diets; however, its role in hypocaloric-diets is unclear. We examined whether increased fiber intake predicts the amelioration in IS and GIIS following a hypocaloric-diet. Methods and Results This is a post-hoc analysis of 55 adult subjects (BMI>27 kg/m 2 ) who completed a 6-month hypocaloric-diet (-500 kcal/day). Dietary intake was assessed using 3-day food records at baseline and post-intervention. We evaluated glucose-induced insulin and C-peptide secretions as AUC of plasma insulin and C-peptide during intravenous-glucose-tolerance tests (IVGTT) and IS via hyperinsulinemic-euglycemic clamps. Data analysis employed regression models and 2-way RM ANOVAs. Post-intervention % change in fiber intake was associated positively with IS clamp (r=0.30) and negatively with % change in total (r=-0.37) and 2 nd phase GIIS IVGTT (r=-0.44) but not C-peptide secretion. It remained associated with lower 2 nd phase GIIS IVGTT after adjustment for sex and % changes in BMI and energy-intake, independently of other macronutrients. Subjects who increased fiber intake (to 28.7±9.0 g/day) had a greater decrease in 2 nd phase GIIS IVGTT, not C-peptide secretion, independently of sex or changes in adiposity or energy-intake compared to subjects who decreased intake (to 20.0±6.8 g/day). Conclusion Higher fiber intake is an independent predictor of reduced 2 nd phase glucose-induced hyperinsulinemia after a hypocaloric-diet. It was not associated with plasma C-peptide, suggesting a role in faster insulin clearance rather reduced insulin secretion. Promoting high-fiber intake may increase the effectiveness of hypocaloric-diets in preventing type 2 diabetes. Registration ISRCTN14476404, BioMedCentral.com. Clinical trial registration This trial was registered at BioMed Central as ISRCTN14476404, on July 28 th , 2017.