Cancers in France in 2015 attributable to high body mass index

Background: Overweight, as defined by high body mass index (BMI), is an established risk factor for various morbidities including cancer. Globally, its prevalence has increased markedly over the past decades. The aim of this study was to estimate the proportion and number of cancers that were attributable to high BMI in France in 2015. Methods: Population attributable fractions (PAFs) and numbers of cancer cases attributable to high BMI (a population mean BMI above the optimum of 22 kg/m(2)) were estimated by age and sex, for cancer sites with convincing or probable evidence of an established causal link. Assuming a 10-year lag-period, PAFs were calculated using mean BMI estimates from a cross-sectional French population survey, and relative risk estimates from published meta-analyses. Results: An estimated 18,639 cancer cases diagnosed in France in 2015 were attributable to high BMI, corresponding to 5.3% of all cancer cases (6.7% in women and 4.1% in men). This included 4507 cases of postmenopausal breast and 3380 cases of colon cancer. The highest estimated PAFs were for oesophageal adenocarcinoma and corpus uteri cancer (37% and 34%, respectively). Conclusion: High BMI is associated with a substantial number of cancer cases in France, a country with a low but increasing prevalence of overweight and obesity when compared to other European countries. Assuming that the association between high BMI and cancer is causal, these results highlight the need to prioritise the prevention of this risk factor as part of cancer control planning in France and elsewhere in Europe.