Previous literature has demonstrated that zinc supplementation has beneficial effects on a wide range of health conditions. Nevertheless, some research suggests that zinc supplementation may promote weight gain and alter adipokine levels, though the findings are inconclusive. Therefore, the purpose of this investigation was to evaluate the potential effects of zinc supplementation on anthropometric indices, body composition, and adipokines. A comprehensive search of electronic databases was conducted from their inception to October 2025to identify eligible randomized controlled trials (RCTs). Relevant data were extracted from the selected studies and subsequently meta-analyzed. Pooled effect estimates were calculated using a random-effects model and expressed as weighted mean differences (WMDs) with corresponding 95% confidence intervals (CIs). A meta-analysis of 41 RCTs (44 effect sizes) indicated that zinc supplementation had no significant overall effect on body mass index (BMI) (WMD: 0.02 kg/m²; p = 0.889), fat mass (FM) (WMD: −0.08 kg; p = 0.794), fat-free mass (FFM) (WMD: 0.41 kg; p = 0.669), adiponectin (WMD: 1.27 µg/mL; p = 0.184), or leptin (WMD: 1.82 ng/mL; p = 0.165). However, zinc supplementation was associated with a significant increase in body weight (BW) (WMD: 0.68 kg; 95% CI: 0.33 to 1.03; p < 0.001) and a reduction in waist circumference (WC) (WMD: −1.03 cm; 95% CI: −1.92 to − 0.13; p = 0.025). According to the GRADE assessment, the certainty of evidence was rated as very high for BW and WC, high for FM, moderate for FFM, and low for BMI, adiponectin, and leptin. This meta-analysis suggests that zinc supplementation has a small effect on BW and WC, but no effect on BMI, FM, FFM, or adipokine levels in the general population. It should be noted that the observed effects of zinc supplementation on body composition were small and not clinically significant. While the certainty of evidence ranged from low to very high across outcomes, the strongest evidence corresponded to minor changes, limiting the clinical relevance of the findings.
Salmani et al. (Fri,) studied this question.