Cancer risk from obesity differs for men and women

New research shows importance of where fat is on the body, with fat around the waist more dangerous for women.

17 December 2020

A new study, co-funded by World Cancer Research Fund (WCRF), Cancer Research UK and Diabetes UK, reveals that where fat is on our body may lead to different health outcomes for men and women. The research revealed that having more body fat around your waist is more dangerous for women than it is for men when it comes to risk of developing colorectal cancer (also known as bowel cancer).

This large study included more than 100,000 people (58,221 people with colorectal cancer and 67,694 controls who did not have colorectal cancer) and was led by researchers at the University of Bristol and the International Agency for Research on Cancer. They found that a higher BMI (body mass index; a measure of total fat) is more dangerous for men, whereas a higher waist-to-hip ratio (your waist circumference divided by your hip circumference; a measure of abdominal fat) is more dangerous for women. To discover this, they used an approach called Mendelian randomisation that uses genetic information as a proxy measure for weight to investigate the effect of different body fat measures on colorectal cancer risk in men and women.

Deadly but preventable

An increase in BMI of about 5kg/m2 raised the risk of colorectal cancer by 23% for men, but only 9% for women. An equivalent increase in waist-to-hip ratio raised the risk for women by 25% but only 5% for men. Colorectal cancer is the fourth most common cancer in the UK but the second deadliest1, yet it is one of the most preventable cancers by eating a balanced diet, being active and maintaining a healthy weight.

Dr Emma Vincent, one of the researchers who led the study and is based at the University of Bristol, said:

“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. 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.”

Dr Anna Diaz Font, Head of Research funding at WCRF, said:

“We know that being overweight or obese increases the risk of at least 12 different types of cancer, including colorectal cancer. 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.”

Natasha Paton, Cancer Research UK’s health information manager, said:

“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. 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 aren’t normal for you tell your doctor. And we’d encourage people to consider taking up bowel cancer screening when invited.”

More research is needed to help understand why this difference between men and women may exist. This study was published in BMC Medicine.


Notes to editors

For more information and media enquiries contact Maxine Lenza, Senior Press and Communications Officer at WCRF, on 07717 131 883 or

About WCRF

World Cancer Research Fund is part of a network of cancer charities with a global reach, dedicated to the prevention and survival of cancer through a healthy diet, maintaining a healthy weight, and being more physically active. By funding and supporting research, developing policy guidance and providing health information, we ensure that people can make informed lifestyle choices to reduce their risk of developing a preventable cancer.

Find out more:
Follow us on social media: TwitterFacebookInstagram