The association between serum zinc level and overweight/obesity: a meta-analysis.

Purpose: The association between serum zinc level and overweight/obesity remains controversial. Hence, we performed a meta-analysis to summarize the relationships.

Methods: A systematic literature search was performed in PubMed, Web of Science and Embase for relevant English articles up to April 20, 2018. The pooled standardized mean difference (SMD) with 95% confidence interval (CI) was calculated with the random-effect model.

Results: For children and adults, the results showed that serum zinc level was significantly lower in the cases compared to controls ([SMD (95% CI): - 1.13 (- 2.03, - 0.23), Z = 2.45, P for Z = 0.014; I = 97.1%, P for I < 0.001] and [SMD (95% CI): - 0.41 (- 0.68, - 0.15), Z = 3.03, P for Z = 0.002; I = 62.9%, P for I = 0.009], respectively). The difference of serum zinc level between overweight adults and controls was not statistically significant [SMD (95% CI): - 0.09 (- 0.27, 0.09), Z = 0.97, P for Z = 0.334; I = 0.0%, P for I = 0.411]. In subgroup analyses, a lower serum zinc level in obese children compared with non-obese controls was observed [SMD (95% CI): - 2.14 (- 3.20, - 1.09)], and the SMD differ significantly between obese adults and controls in the case-control studies [SMD (95% CI): - 0.49 (- 0.90, - 0.08)].

Conclusion: Our meta-analysis suggested that the serum zinc level was significantly lower in obese children and adults. More large observational studies are required to confirm these results in future research.