The effect of curcumin supplementation on weight loss and anthropometric indices: an umbrella review and updated meta-analyses of randomized controlled trials

Background: Curcumin supplementation may promote weight loss and ameliorate obesity-related complications through its antioxidative and anti-inflammatory properties. Objective: An umbrella review and updated meta-analysis of randomized controlled trials (RCTs) was conducted to evaluate the effect of curcumin supplementation on anthropometric indices. Methods: Systematic reviews and meta-analyses (SRMAs) of RCTs were identified from electronic databases (Medline, Scopus, Cochrane, and Google Scholar) up to 31 March, 2022, without language restriction. SRMAs were included if they assessed curcumin supplementation on any of the following: BMI, body weight (BW), or waist circumference (WC). Subgroup analyses were performed, stratifying by patient types, severity of obesity, and curcumin formula. The study protocol was a priori registered. Results: From an umbrella review, 14 SRMAs with 39 individual RCTs were included with a high degree of overlap. In addition, searching was updated from the last search of included SRMAs in April 2021 up to 31 March, 2022, and we found 11 additional RCTs, bringing the total up to 50 RCTs included in the updated meta-analyses. Of these, 21 RCTs were deemed of high risk of bias. Curcumin supplementation significantly reduced BMI, BW, and WC with mean differences (MDs) of −0.24 kg/m² (95% CI: −0.32, −0.16 kg/m²), −0.59 kg (95% CI: −0.81, −0.36 kg), and −1.32 cm (95% CI: −1.95, −0.69 cm), respectively. The bioavailability-enhanced form reduced BMI, BWs, and WC more, with MDs of −0.26 kg/m² (95% CI: −0.38, −0.13 kg/m²), −0.80 kg (95% CI: −1.38, −0.23 kg) and −1.41 cm (95% CI: −2.24, −0.58 cm), respectively. Significant effects were also seen in subgroups of patients, especially in adults with obesity and diabetes. Conclusions: Curcumin supplementation significantly reduces anthropometric indices, and bioavailability-enhanced formulas are preferred. Augmenting curcumin supplement with lifestyle modification should be an option for weight reduction. This trial was registered at PROSPERO as CRD42022321112 (https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022321112).