The recent IARC report on cancer prevention concludes that the absence of body fatness lowers cancer risk, and that intentional weight loss (based largely on research from animal studies) has a causal cancer preventive effect. Never too late to start weight management strategies…or indeed too early.
Data on BMI in childhood, adolescence and early adulthood show an association with several cancers associated with adult BMI. This doesn’t mean that all cancer risk is developed in early life, but does suggest an even greater reason to avoid weight gain in adult life.
For female cancers the IARC report provides lots of reasons why women should be supported for weight management. For cancer risk reduction in post-menopausal breast cancer, avoiding excess weight and avoiding body-weight gain in adulthood are key features, even in women aged over 50 years. Ovarian cancer has a similar profile. The potential reduction for endometrial cancer was estimated to be exceedingly high (RR 7.14 (6.33-8.06) highest versus normal BMI) especially in women who had never used HRT.
Most Scots are aware of tobacco as a cancer risk factor but just how many know (or believe) that avoiding extra weight means reducing cancer risk of 13 cancers: colon, oesophageal, kidney, breast (post-menopausal), uterus, stomach, liver, gall bladder, pancreas, ovary, thyroid, multiple myeloma and meningioma.
How many know (or believe) that avoiding extra weight means reducing cancer risk of 13 cancers?
When we interviewed women attending routine breast screening clinics about lifestyle and breast cancer risk, they were sceptical saying “(cancer) if it’s for you, it won’t go by you” and “Sometimes it just seems the luck of the draw…” Clearly, there is much work to do in raising awareness about cancer risk reduction. Obesity and cancer are public health issues that do not get much air time in public health agendas, and unless we spell out the very positive opportunity about risk reduction, we may fail to get the support needed for effective action against cancer which includes obesity prevention and management.
Many healthcare staff are also sceptical about the role of weight management in risk reduction and highlight lack of evidence to support action. The reality is that we will never have randomised controlled trials of body weight and the development of primary cancer (with the possible exception of Lynch syndrome patients) because of the need for long term lifestyle adherence and the many years that would be needed for follow up. The IARC report has used a wide portfolio of evidence that is available including cohort studies, case controls, Mendelian randomisation, evidence from experimental animal studies and detailed mechanistic evidence. There is no lack of evidence, there is a great deal of consistency, and there is a clear message that says if we avoid excess body fat, we can reduce cancer – it is a message we need to disseminate widely and one that needs to be heard loud and clear.
Professor Annie S. Anderson
Member, IARC working group on body fatness and obesity, Co-Director, Scottish Cancer Prevention Network and Professor of Public Health Nutrition, University of Dundee.