Obesity is strongly linked to the risk of developing certain major cancers, according to a re-analysis of research published in The BMJ | OnMedica | BMJ
Links between obesity and cancer risk are strongest for 11 cancers related to digestive organs and hormones, says the review. Obesity could also be linked to other cancers, but the quality of the evidence is not sufficiently strong to draw those conclusions yet.
Obesity prevalence has more than doubled over the past 40 years, and the evidence to date suggests that it is linked to a heightened risk of developing particular cancers, but methodological flaws in some published studies have weakened the strength of the associations found.
To better gauge the quality of the evidence and the strength of these associations, the researchers comprehensively reviewed published studies looking at obesity and cancer risk.
From among 204 reviews that analysed obesity measurements, such as body mass index (BMI), weight gain, and waist circumference, and the risk of 36 cancers, 95 included continuous measures of obesity.
Only 13% of the associations for nine cancers were based on strong evidence, meaning the results were statistically significant and excluded bias.
Strong associations were found in studies that looked at heightened risk of oesophageal, bone marrow, colon (in men), rectal (in men), biliary tract system, pancreatic, endometrial (in premenopausal women), and kidney cancers.
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Link to the research: Kyrgiou M, Kalliala I, Markozannes G, et al. Adiposity and cancer at major anatomical sites: umbrella review of the literature. BMJ 2017;356:j477. DOI: 10.1136/bmj.j477