ABSTRACT
BACKGROUND AND AIMS: Insulin resistance in adolescents is a major health concern. The aim of this study was to evaluate the effect of grape seed extract on insulin resistance in adolescents with metabolic syndrome (MetS). METHODS: Participants were divided into grape seed extract (GSE) and placebo groups (n = 24 each) and received 100 mg/day of GSE or placebo and were placed on a weight loss diet for 8 weeks. Anthropometric and biochemical indices, blood pressure, dietary intake, and physical activity were measured before and after the intervention. RESULTS: Forty-two participants completed the trial. After the intervention, the age, sex, baseline values, energy intake and physical activity as a covariate adjusted using ANCOVA for determine differences between groups. The MD (mean difference ±SEM) of HOMA-IR between the GSE group (-1.46 ± 0.45) and the placebo group (-0.48 ± 0.47), (p = 0.020), and the MD of insulin between the GSE group (-7.05 ± 2.11) and the placebo group (-1.71 ± 2.12), (p = 0.024), were significant. Although changes were observed in other variables, they were not statistically significant. CONCLUSIONS: GSE improves insulin concentration and insulin resistance in adolescents with MetS and provides a basis for possible application of the GSE in the clinical management of MetS in adolescents. This study registered under Randomized Clinical Trials.gov Identifier no. IRCT2013112611288N7.