An umbrella review has found strong support for associations between obesity and 11 cancers, including kidney cancer, esophageal adenocarcinoma, multiple myeloma, and cancers of the gastric cardia, colon, rectum, biliary tract system, pancreas, breast, endometrium, and ovary. Obesity’s relationship with other cancer types, if any, remains unclear.

The link between obesity and kidney cancers has been corroborated by recent reviews from the World Cancer Research Fund and the International Agency for Research on Cancer.

For the umbrella review, Maria Kyrgiou, MD, of Imperial College London and colleagues, collected 204 meta-analyses that examined the risk of developing or dying from 36 types of cancer. Of these, they identified 12 meta-analyses and systematic reviews of cohort studies that used adiposity as a continuous variable, had the strongest P values, and had the lowest risk of bias.

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For every 5 kg/m2 increase in body mass index, the risks for kidney cancer rose by 30%. The risk increase for the other 10 cancers ranged from 9% for rectal cancer in men to 56% for biliary tract system cancer. The risk for postmenopausal breast cancer not due to hormone replacement therapy rose by 11% for each 5 kg women gained in adulthood, and the risk for endometrial cancer rose by 21% for each 0.1 increase in the waist-to-hip ratio. The team considered the possible influences of sex, menopause, smoking, and hormone replacement therapy. They did not evaluate the quality of individual studies included in the original meta-analyses, which is a limitation.

“Obesity is becoming one of the biggest problems in public health; evidence on the strength of the associated risks may allow finer selection of those at higher risk of cancer, who could be targeted for personalized prevention strategies,” Dr Kyrgiou and her team concluded in BMJ.

In an accompanying editorial, Yikyung Park, ScD, and Graham A. Colditz, MD, DrPh, of Washington University School of Medicine in St Louis, Missouri, noted, “Given the critical role of healthcare providers in obesity screening and prevention, clinicians…can be a powerful force to lower the burden of obesity related cancers, as well as the many other chronic diseases linked to obesity such as diabetes, heart disease, and stroke. The data are clear. The time for action is now.”

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1.   1. Kyrgiou M, Kalliala I, and Markozannes G. Adiposity and cancer at major anatomical sites: umbrella review of the literature. BMJ 2017; 356:j477. doi: 10.1136/bmj.j477

2.   2. Park Y and Colditz GA. Fresh evidence links adiposity with multiple cancers: The association is now clear; it’s time to get serious about prevention. BMJ 2017;356:j908 doi: 10.1136/bmj.j908