Effects of Intermittent Fasting, Ketogenic Diets, and Low-Carbohydrate Diets on Body Composition in Adults with Overweight or Obesity: A Meta-Analysis of Clinical Trials

Background: Intermittent fasting, ketogenic diets, and carbohydrate restriction can alter body weight and body composition, but loss of adipose and lean tissue must be distinguished. Objective: To summarize the reported effects of dietary interventions on body weight or body mass index (BMI), total fat mass, visceral or central adiposity, and lean or muscle mass among adults with overweight or obesity. Methods: Controlled dietary intervention studies were described in the source systematic review following PRISMA guidance. Outcome estimates and heterogeneity were transcribed from its study-specific supplementary forest plots. Results: The supplementary syntheses reported 21 estimates for weight/BMI (SMD -0.97, 95% CI -1.07 to -0.86; I² 79.66%), nine for total fat mass (-0.94, -1.06 to -0.81; I² 27.86%), eight for visceral or central adiposity (-0.80, -0.98 to -0.63; I² 74.16%), and eleven for lean/muscle mass (-0.08, -0.48 to 0.31; I² 96.48%). The original manuscript and descriptive tables give inconsistent total participant counts. Conclusions: The available summary effects favor lower weight and fat-related indicators, whereas pooled lean-mass effects are inconclusive. Clinical interpretation is constrained by intervention diversity, different body-composition measurements, extensive lean-mass heterogeneity, and original uncertainty in the computation of some study-level standard errors.