The effect of reduced carbohydrate diet on cardiometabolic risk factors and gut microbiota in children and adolescents with obesity: a randomized controlled trial

Abstract

Abstract Objective To compare the effects of a reduced-carbohydrate diet (RCD) with a standard diet (STD) on cardiometabolic risk factors and gut microbiota composition in children and adolescents with obesity. Methods In this randomized controlled trial, 84 children and adolescents with obesity, aged 7–16 years, were randomly assigned to either a RCD (30–40% of total energy from carbohydrates, emphasizing high‑fiber sources) or a STD for 12 weeks. A calorie deficit was applied in both groups. Dietary assessments, anthropometric measurements, body composition analysis, biochemical measurements, and gut microbiota composition were evaluated at baseline and at the end of follow-up. Change in body mass index at 12 weeks was considered the primary outcome. Results Sixty-one participants (72.6%) completed the intervention. Both the reduced-carbohydrate diet (RCD) and standard diet (STD) groups showed significant reductions in BMI, BMI z-score, waist circumference, and percent body fat over the 12-week intervention, with no significant differences between groups ( p > 0.05).Triglyceride levels and the triglyceride-to-HDL cholesterol ratio decreased significantly in the RCD group compared with the STD group (between-group mean difference − 40.31 mg/dL, 95% CI − 73.79 to − 6.82, p = 0.019 for TG; − 1.03, 95% CI − 1.85 to − 0.20, p = 0.016 for TG/HDL-C). The relative abundance of Verrucomicrobia increased in the RCD group, whereas it decreased in the STD group. Conclusions The reduced carbohydrate diet did not show superiority to standard diet in reducing anthropometric indices. However, reduced carbohydrate diet showed beneficial effects on Triglyceride levels and Triglycerides to high-density lipoprotein cholesterol ratio. Further investigation of gut microbiota composition is needed. Trial registration Iranian Registry of Clinical Trials (IRCT), IRCT20180805040703N2, retrospectively registered on 7 May 2022.