Adiposity and cancer: systematic review and meta-analysis.

Obesity is a major health challenge. Here we show that body mass index is positively associated with risk of 19 cancers and inversely associated with 3, based on a systematic review and meta-analysis of prospective studies of 25 cancer types. We searched PubMed, EMBASE and Scopus through to 23 April 2025, identifying 226 articles comprising 1.5 million incident cancers. We identified positive associations for leukaemia, non-Hodgkin lymphoma, bladder cancer and glioma, not previously identified by major consensus reports. Associations differed according to region and sex, with stronger associations for postmenopausal breast and ovarian cancers in East Asia, weaker associations for gallbladder cancer in East Asia and in men, and stronger associations for colorectal cancer in men. Body mass index and waist circumference showed similar associations with cancer. We reviewed Mendelian randomization and imaging-based studies; genetic findings were generally consistent with observational associations, while imaging data were limited. Our findings underscore the impact of obesity on cancer risk.