Adult weight gain and adiposity-related cancers: a dose-response meta-analysis of prospective observational studies

Backgrounds: Considerable evidence suggests that adiposity, measured by body mass index, is implicated in carcinogenesis. While adult weigh gain has diverse advantages over body mass index in measuring adiposity, systematic reviews on adult weight gain and risks of major cancers are lacking. Methods: PubMed and Embase were searched from the inception to May, 2014 to identify prospective observational studies investigating the relationship between adult weight gain and incident cancers of the breast, prostate, and colorectum. Dose-response meta-analyses were performed using a random-effects model to estimate summary relative risk (RR) and 95% confidence interval (CI) for each cancer type. Results: In the linear dose-response estimating cancer risk associated with 5kg increase in adult weight gain, a statistically significant direct association was found only for postmenopausal breast cancer and colon cancer. The summary RR was 1.11 (95% CI=1.08-1.13, I2=22%, seven studies with 4,570 cases, range=0-35kg) for postmenopausal breast cancer; 0.99 (95% CI=0.95-1.03, I2=36%, three studies with 2,409 cases, range=0-27.5kg) for premenopausal breast cancer. Etiologic heterogeneity by menopausal status at diagnosis was statistically significant (Pheterogeneity=0.001). The summary RR for colon cancer was 1.06 (95% CI=1.03-1.10, I2=0%, four studies with 2,909 cases, range=0-29kg). While there was no evidence of heterogeneity by sex (Pheterogeneity=0.17), the association was statistically significant only among men. No evidence of a linear association was indicated for prostate cancer (RR=0.98, 95% CI=0.94-1.02, four studies with 6,882 cases, range=0-25kg) and for its subtypes (localized: RR=0.96, 95% CI=0.92-1.00, I2=38%; advanced: RR=1.04, 95% CI=0.99-1.09, I2=0%). Conclusions: Avoiding adult weight gain itself may confer protection against postmenopausal breast cancer and colon cancer. As preventing weight gain is relatively more feasible than losing weight, clinicians and public health policies may prioritize weight maintenance throughout adulthood to reduce the burden of postmenopausal breast cancer and colon cancer.