Insulin Resistance Predicts the Effectiveness of Different Glycemic Index Diets on Weight Loss in Non-Obese Women

Abstract

Objective: The present study aimed to evaluate whether baseline insulin resistance (IR) modify weight change associated to glycemic index (GI) of the diet. Method: This is a secondary analysis of a randomized GI intervention according to baseline HOMA-IR. Middle-aged (25–45 years), non-obese (BMI 23–29.9 kg/m²) women were randomized to low or high GI diets matched on total energy, macronutrient composition, and fiber content. Both groups received dietary counseling based on a small energy restriction (100–300 kcal/day). Women were classified in two groups according to their baseline HOMA-IR: IR (n = 64) and non-IR (n = 121). Results: At baseline, IR and non-IR groups had similar BMI (26.7 vs. 26.3 kg/m²; p = 0.21), but the IR group presented with higher waist circumference (82.7 vs. 80.8 cm; p = 0.02) and showed greater weight loss after 12 months of follow-up (–1.6 vs. –1.1 kg; p = 0.01), mainly among those in a high-GI diet (–2.1 vs. –1.0 kg; p = 0.005) compared to the non-IR group (–1.4 vs. –0.8 kg; p = 0.04). Conclusions: The high-GI group showed statistically significant higher reduction in body weight, mainly among those women with baseline IR . Low-GI diet did not facilitate weight loss neither in IR women nor in non-IR women.