Body mass index and the risk of cancer in women compared with men: a meta-analysis of prospective cohort studies.

Studies investigating the association between BMI and the risk of the common cancers in men or women have reported inconsistent results. We searched the PubMed, Embase, and Cochrane Library electronic databases for relevant articles published until April 2015. Overall, we analyzed 128 datasets (51 articles), including 154 939 incident cancer cases. The pooled relative risk ratio (RRR) (female to male) showed that the relative risk of overweight associated with colorectal [RRR: 0.91; 95% confidence interval (CI): 0.85-0.97] or rectal cancer (RRR: 0.94; 95% CI: 0.88-0.99) was significantly lower in women than in men. However, the relative risk of overweight associated with lung (RRR: 1.14; 95% CI: 1.06-1.22) or kidney cancer (RRR: 1.15; 95% CI: 1.05-1.26) was significantly higher in women than in men. Furthermore, the relative risk of obesity associated with liver (RRR: 0.71; 95% CI: 0.51-0.99), colorectal (RRR: 0.83; 95% CI: 0.75-0.93), colon (RRR: 0.73; 95% CI: 0.68-0.0.78), rectal (RRR: 0.84; 95% CI: 0.76-0.92), and kidney cancer (RRR: 1.20; 95% CI: 1.06-1.37) differed significantly between women and men. Finally, the relative risk of underweight associated with gastric (RRR: 0.83; 95% CI: 0.70-0.97), liver (RRR: 0.83; 95% CI: 0.71-0.97), and gallbladder cancer (RRR: 1.25; 95% CI: 1.04-1.49) differed significantly according to sex. In conclusion, our study showed that the association between BMI and the risk of several cancers was significantly different between the sexes. For some cancer types, the sex difference was affected by country, sample size, follow-up duration, and study quality.