A higher body mass index (BMI) increases the risk of cancer for men and a higher waist-to-hip ratio increases the risk for women, according to a study of over 100,000 people led by researchers at the University of Bristol and the International Agency for Research on Cancer.
"Our study, which is the largest to look at the difference between body fat and colorectal cancer risk in men and women, reveals the need for a more nuanced approach when trying to prevent cancer,” explained Dr Emma Vincent, one of the researchers who led the study from the University of Bristol. “We are now working to understand exactly how increased body fat causes colorectal cancer, which may give us new targets for reducing risk. This is important because maintaining weight loss is still very difficult."
It is known that higher adiposity increases the risk of colorectal cancer (CRC) however, whether this relationship varies by anatomical sub-site or by sex is unclear, and the metabolic alterations mediating the effects of adiposity on CRC are not fully understood. The study, ‘Adiposity, metabolites, and colorectal cancer risk: Mendelian randomization study’, examined sex- and site-specific associations of adiposity with CRC risk and whether adiposity-associated metabolites explain the associations of adiposity with CRC.
They found that an increase in BMI of about 5 kg/m2 raised the risk of colorectal cancer by 23 percent for men, but only nine percent for women. Whereas an equivalent increase in waist-to-hip ratio raised the risk for women by 25 percent, this was only five percent for men.
"We know that being overweight or obese increases the risk of at least 12 different types of cancer, including colorectal cancer,” said Dr Anna Diaz Font, Head of Research funding at World Cancer Research Fund International. “But this new research reinforces how important it is to include a wide and diverse range of people in research studies, as we don't yet fully know the differences gender or race may play when it comes to risk of cancer."
"It's well established that keeping a healthy weight affects many types of cancer. Most research linking excess weight to cancer uses BMI, but this study adds to the evidence that carrying excess fat around the waist is also important,” added Natasha Paton, Cancer Research UK's health information manager. “People can reduce their risk of bowel cancer by keeping a healthy weight, eating a diet with lots of fibre and less red and processed meat, drinking less alcohol, and not smoking. Diagnosing bowel cancer early saves lives, so if you notice any changes that are not normal for you tell your doctor. And we'd encourage people to consider taking up bowel cancer screening when invited."
The investigators added that more research is needed to help understand why this difference between men and women may exist.
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