BMI associated with 'substantial' cancer risk, warn researchers

People who are obese or overweight face a significantly higher risk of developing 10 of the most common cancers, according to a large-scale study.

Obesity: link to cancer
Obesity: link to cancer

Researchers estimate that as many as 41% of uterine cancer cases and 10% of gallbladder, kidney, liver and colon cancers could be directly attributable to a patient’s weight – equivalent to over 12,000 cancer cases every year.

The UK study, conducted by researchers at the London School of Hygiene and Tropical Medicine and published in The Lancet, followed 5.24m cancer-free patients for an average period of seven and a half years. Nearly 167,000 developed cancer in this time.

For certain cancers, each 5kg/m2 increase in BMI was associated with a step increase in the risk of developing them, including cancer of the uterus by 62%, gallbladder by 31%, kidney by 25% and a roughly 10% increase in cervix, thyroid and leukaemia cancers.

Higher BMI was also found to increase the overall risk of developing liver, colon, ovarian and postmenopausal breast cancers, but there was some evidence that having a higher BMI could slightly reduce the risk of prostate and premenopausal breast cancer.

Increasing BMI linked to rise in cases

Based on their results, the authors warned that a 1kg/m2 increase in average BMI could contribute to an additional 3,790 cases of these 10 cancers in the UK every year.

Study leader Dr Krishnan Bhaskaran said: ‘The number of people who are overweight or obese is rapidly increasing both in the UK and worldwide. It is well recognised that this is likely to cause more diabetes and cardiovascular disease. Our results show that if these trends continue, we can also expect to see substantially more cancers as a result.

‘There was a lot of variation in the effects of BMI on different cancers. For example, risk of cancer of the uterus increased substantially at higher body mass index; for other cancers, we saw more modest increases in risk, or no effect at all.

'For some cancers like breast cancer occurring in younger women before the menopause, there even seemed to be a lower risk at higher BMI. This variation tells us that BMI must affect cancer risk through a number of different processes, depending on the cancer type.’

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