Studying the link between physical activity, body fat and cancer risk

Background

Bowel cancer (which includes cancer of the colon or rectum) is one of the most common cancers in Australia. Almost 17,000 new cases are diagnosed each year. The risk factors for bowel cancer include older age, colonic polyps, bowel diseases, strong family history and rare genetic disorders. Lifestyle factors such as being overweight or obese, having a diet high in red meat, drinking alcohol and smoking also put people at higher risk of bowel cancer.

Prolonged sitting is also emerging as a potential risk factor for these cancers, but little is known about the interactive effects of obesity, physical activity and prolonged sitting on cancer risk. This analysis assessed independent and interactive effects of physical activity, body mass index (BMI), as a proxy for body fat, and sitting time on bowel cancer risk.

The research

The researchers looked at data of more than 200,000 people in NSW with the aim to find out if physical activity, obesity and prolonged sitting influenced someone’s risk of colon and rectal cancer. The team found that any amount of vigorous physical activity, even just over 10 minutes a day, reduced study participants’ risk of colon cancer by 22%. They also found that being obese increased individual’s risk of developing colon cancer by 32%.

Since physical activity can also contribute to weight loss, which can help people manage the cancer risk that comes from being overweight or obese, the study also examined if the risks of being obese were offset by the benefits of physical activity, or vice versa. The team discovered that the two risk factors, physical activity and obesity, appear to be independent of each other. This means that anyone can benefit from physical activity, regardless of their body weight, and this can effectively reduce their risk of colon cancer.

The impact

The findings show that everyone can lower their risk of cancer by making changes to daily routine such as being more physically active, regardless of their body weight. It is known that 1 in 3 cancer cases in Australia can be prevented by living a healthy lifestyle, so people should be encouraged to be physically active, as well as achieve and maintain a healthy weight. It is a simple and effective strategy everyone should seek to implement to reduce their risk of bowel cancer.