Abstract
Recently, obesity has become a common worldwide concern. Leptin, as an adipocytokine,
plays a major role in the etiology of obesity. Prior studies have demonstrated that
zinc potentially affects serum leptin levels. However, clinical trials carried out
in this regard are not consistent. Therefore, current meta-analysis was conducted
to ascertain the actual effect of zinc supplementation on serum leptin levels in adults.
Databases of PubMed, SCOPUS, and Google Scholar were methodically searched to identify
relevant articles up to April 2018. Clinical trials that examined the effect of zinc
supplementation on serum leptin concentrations as outcome variables in human adults
were included. The mean difference (SD) of leptin changes in the intervention and
placebo groups were used to calculate the overall effect size. Totally, 663 articles
were identified, of which 6 studies were eligible randomized controlled trials (RCTs)
with 7 treatment arms. The analysis suggested that zinc supplementation exerts no
significant effect on overall serum leptin (WMD: 0.74 ng/ml; 95% CI: −1.39 to 2.87,
p=0.49). Nevertheless, sex and duration of intervention seemed to impact the extent
of zinc’s influence. In trials with female subjects, zinc consumption led to a significant
decrease in serum leptin level (WMD: −1.93 ng/ml; 95% CI: −3.72 to −0.14, p=0.03)
as well as trials that lasted for more than 6 weeks (WMD: −1.71 ng/ml; 95% CI: −3.07
to −0.35, p=0.01), in comparison to the control group. Zinc supplementation did not
significantly improve leptin concentrations, but it may result in a decreased circulating
leptin level in studies with a duration of more than 6 weeks especially among females.
Key words
zinc - supplementation - leptin - meta-analysis