To provide a comprehensive synthesis of the effects of Zn supplementation on childhood body composition and adiposity-related hormone levels.

Five electronic databases were searched for randomized controlled trials of Zn supplementation studies published before 28 February 2015. No statistical pooling of results was carried out due to diversity in study designs.

Community- or hospital-based, from fourteen developing and developed countries.

Children and adolescents aged 0 to 10 years.

Seven of the fourteen studies reported an overall or subgroup effect of Zn supplementation on at least one parameter of body composition, when determined by anthropometric measurements (increased mid upper-arm circumference, triceps skinfold, subscapular skinfold and mid upper-arm muscle area, and decreased BMI). Three out of the fourteen studies reported increased mean value of total body water estimated by bio-impedance analysis and increased fat-free mass estimated by dual energy X-ray absorptiometry and by total body water. Zn supplementation was associated with increased fat-free mass among stunted children. One study found supplementation decreased leptin and insulin concentrations.

Due to the use of anthropometry when determining body composition, a majority of the studies could not accurately address whether alterations in the fat and/or fat-free mass components of the body were responsible for the observed changes in body composition. The effect of Zn supplementation on body composition is not consistent but may modify fat-free mass among children with pre-existing growth failure.