Effect of Exogenous Ketones as an Adjunct to Low-Calorie Diet on Metabolic Markers.

BACKGROUND/OBJECTIVES: Overweight and obesity affect a majority of adults, contributing to metabolic disorders. Caloric restriction often leads to undesirable lean mass loss alongside fat reduction. This study investigated whether exogenous β-hydroxybutyrate (BHB) supplementation, as an adjunct to a hypocaloric diet, improves body composition and metabolic markers in overweight and obese adults by preferentially reducing fat mass while preserving lean mass. METHODS: In this 8-week randomized, double-blind, placebo-controlled trial, 51 adults were assigned to receive either racemic BHB mineral salts or placebo (maltodextrin) twice daily, alongside modest caloric restriction. Assessments at baseline and week 8 included dual-energy X-ray absorptiometry for body composition, indirect calorimetry for resting metabolic rate (RMR), and venous blood analyses for cardiometabolic biomarkers (e.g., lipids, HOMA-IR, uric acid, liver enzymes). RESULTS: Body mass decreased in both groups over the intervention (p < 0.01 within placebo and p < 0.001 within BHB). Within the BHB group, fat mass decreased significantly (-2 kg; p < 0.05 vs. baseline), body fat percentage improved (p < 0.01 vs. baseline), and lean-to-fat mass ratio increased (p < 0.05 vs. baseline); no such significant changes were observed within the placebo group. Group × time interactions were not significant for these body composition variables (p > 0.05). Furthermore, lean mass was largely preserved, with no declines in RMR. Within the BHB group, LDL cholesterol was reduced (p < 0.05 vs. baseline), while other lipids, HOMA-IR, and uric acid remained stable, with liver enzymes showing a positive change. CONCLUSIONS: Exogenous BHB supplementation may enhance the quality of diet-induced weight loss through within-group improvements in fat mass reduction and lean mass preservation, with no adverse metabolic impacts.