Calcium Beta‐Hydroxy‐Beta‐Methylbutyrate‐Enriched Nutritional Supplementation During Dietary Weight Loss in Adults With Obesity: A Randomized Controlled Trial

Background Dietary and pharmacologic weight loss can reduce skeletal muscle. Whether calcium beta‐hydroxy‐beta‐methylbutyrate (CaHMB)‐enriched supplementation preserves muscle while promoting fat loss in adults with obesity remains uncertain. We evaluated a CaHMB‐enriched nutritional supplement during energy restriction. Methods In this randomized, double‐blind, controlled trial, 102 Chinese adults with obesity (body mass index [BMI] ≥ 28 kg/m 2 ) were assigned 1:1 to a CaHMB‐enriched nutritional supplement (65 g/day powder containing 3.0 g/day CaHMB and 24 g/day protein) or an energy‐matched maltodextrin control for 12 weeks, alongside standardized dietary energy restriction. The primary outcome was change in whole‐body skeletal muscle mass (SMM) by multifrequency bioelectrical impedance analysis. Secondary outcomes included visceral fat area (VFA), body fat mass (BFM), basal metabolic rate (BMR), physical function and metabolic biomarkers. ITT analyses adjusted for baseline values, age, sex, dietary intake and physical activity changes. Results Participants had a mean age of 36.8 ± 5.2 years, a mean BMI of 32.2 ± 3.3 kg/m 2 and 37.3% (38/102) were female. The CaHMB group maintained SMM (median +0.7 kg; IQR = −0.2 to 2.0), whereas the control group lost SMM (median = −0.6 kg; IQR = −1.9 to −0.1; between‐group difference 1.3 kg; 95% CI = 0.5 to 1.9; p < 0.001). More CaHMB participants gained ≥ 0.5 kg SMM (52.9% vs. 11.8%; OR = 8.44; 95% CI = 3.23 to 25.22; p < 0.001). CaHMB also produced greater reductions in VFA (adjusted mean difference [AMD] = −14.9 cm 2 ; 95% CI = −25.1 to −4.5; p = 0.004) and BFM (AMD = −4.9 kg; 95% CI = −6.8 to −3.1; p < 0.001), preserved BMR (difference 62.0 kcal/day; 95% CI = 35.0 to 89.0; p < 0.001) and reduced fasting glucose more than control (difference −0.4 mmol/L; 95% CI = −0.8 to −0.1; p = 0.009). No adverse events were reported. Conclusions During dietary weight loss, CaHMB‐enriched supplementation preserved SMM and produced greater visceral and total fat reductions. Because the intervention also contained protein, longer factorial trials are needed to isolate CaHMB‐specific effects. Trial Registration ClinicalTrials.gov identifier: NCT04953936