To systematically evaluate the relationship of exposure to five heavy metals, namely lead, arsenic, cadmium, mercury and aluminum with obesity in children and adolescents, so as to provide a scientific basis for subsequent research in the area.

Four Chinese databasesc (CBM, VIP, CNKI and Wanfang) and four foreign databases (OVID, PubMed, Web of Science and EBSCO), were searched to collect relevant studies, and the search period was from the establishment of the database to May 5, 2024. After 2 investigators independently screened the literature, extracted the data and evaluated the risk of bias of the included studies, the results were analyzed quantitatively and summarized qualitatively.

A total of 5 cohort studies on lead exposure and 17 cross-sectional studies involving exposure to lead (n=13), cadmium (n=8), mercury (n=8), arsenic (n=4), and aluminum (n=1) were included. Meta analysis of the 2 cohort studies showed that lead exposure was not associated with the risk of overweight and obesity in children (RR=0.76, 95%CI=0.50-1.16, P > 0.05). The cross-sectional study Meta-analysis results showed that lead exposure was negatively associated with the risk of childhood overweight (OR=0.70, 95%CI=0.59-0.84, 2 studies) and obesity (OR=0.71, 95%CI=0.58-0.87, 3 studies); cadmium exposure was negatively associated with the risk of childhood overweight (OR=0.83, 95%CI=0.73-0.95, 2 studies) and obesity risk(OR=0.70, 95%CI=0.63-0.78, 3 studies); mercury exposure increased the risk of overweight/obesity (OR=1.42, 95%CI=1.14-1.76, 2 studies) and abdominal obesity (OR=1.99, 95%CI=1.45-2.73, 2 studies) in children; the group with the highest concentration of arsenic in urine had a lower risk of developing obesity compared to the group with the lowest concentration (OR=0.39, 95%CI=0.23-0.65, 1 study), and the group with the highest concentration of aluminum in urine had a lower risk of obesity compared with the group with the lowest concentration (OR=0.52, 95%CI=0.31-0.86, 1 study)(all P < 0.05).

Heavy metal exposure may be a risk factor for overweight and obesity in children and adolescents, but the conclusions are inconsistent and need to be validated in further high-quality prospective cohort studies.