Context
Inconsistent results have been reported regarding the effects of different types of algae, such as Spirulina and Chlorella, on anthropometric indices.

Objective
To conduct a meta-analysis to assess the efficacy of algae supplementation on anthropometric indices.

Data Sources
A comprehensive systematic search was conducted to find relevant articles published from January 1990 to January 2024.

Data Extraction
Randomized controlled trials (RCTs) comparing algae supplementation with a placebo or control group were included. The risk of bias and certainty of the evidence were evaluated using the Cochrane risk-of-bias tool and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology, respectively. The random-effects model was used to find the Weighted mean differences (WMDs) for each outcome.

Data Analysis
Of 9079 distinct articles in the initial screening, 61 clinical trials were included in this meta-analysis. Algae supplementation resulted in lower body mass index (WMD, –0.27 kg/m2 (95% CI, –0.42 to –0.13); GRADE rating, low), body weight (WMD: −0.78 kg [–1.18 to –0.38]; GRADE rating, low), waist circumference (WMD, –0.68 cm [–1.27 to –0.10]; GRADE rating, very low), kilograms of body fat (WMD, –0.65 kg [–1.13 to –0.17]; GRADE rating, low), and body fat percentage (WMD, –0.9% [–1.62 to –0.17]; GRADE rating, very low) compared with placebo or controls. Nevertheless, the statistically significant effects of algae supplementation on hip circumference (WMD, –0.20 cm [–0.73 to 0.32]; GRADE rating, moderate), waist to hip ratio (WMD, –0.01 [–0.01 to 0.00]; GRADE rating, moderate), and lean body mass (WMD, –0.30 kg [–0.62 to 0.02]; GRADE rating, moderate) were not observed.

Conclusions
Overall, the findings of this meta-analysis indicate supplementation with algae may exert beneficial effects on anthropometric indices. However, due to between-studies heterogeneity and very low to low levels of GRADE for significant outcomes, the results should be interpreted with caution.