Association between body mass index and major cancers with a focus on breast in South and Southeast Asia: A regional systematic review and meta-analysis

Objectives: We investigated the association between body mass index (BMI) and cancer at different sites among adults in South and Southeast Asia in a systematic review. Material and Methods: We conducted an electronic database search on PubMed, Embase, CINAHL, and Web of Science, in accordance with the PROSPERO protocol (registration No. CRD42023427644). Studies that reported the association of BMI and cancer incidence in South and Southeast Asian countries were included. We assessed the quality of the studies using the Newcastle-Ottawa Scale. Potential differences in the definition of BMI categories were considered. We performed random-effects meta-analysis to estimate the pooled effect size using Stata 17. Findings: Of the 1,361 records identified, in the final analysis, 46 studies from 19 countries met the pre-specified inclusion criteria. The meta-analysis focused on 26 studies on breast cancer. Out of 46 studies, 95% were of high or moderate quality. We found an association between breast cancer and overweight (odds ratio (OR), 1.29; 95% CI: 1.02-1.64, I2=87.31%; 19 studies) and obesity (OR, 1.82; 95% CI:1.21-2.75, I2=87.68%; 14 studies). Results for other cancers were too sparse for a meta-analysis. A positive association was observed between BMI and other cancers like colorectal, lung, oral, endometrial, cervical, esophageal, and gastric cancer; data were insufficient to perform a meta-analysis. Conclusion: Our findings suggest that obesity is associated with breast cancer in South and Southeast Asia. More high-quality research is needed to confirm this relationship and to support future public health efforts to promote a healthy BMI in the region.