Taking regular exercise is going to become increasingly important in helping to prevent cancers as the UK emerges from lockdown, say scientists.
Since the pandemic began a year ago, growing numbers of people have reported gaining weight after cutting down on physical activity while others say they have been eating more junk food.
Being overweight or obese leaves individuals vulnerable to tissue damage and the development of tumours, with more than a dozen types of cancer having been linked to excess weight in recent research studies.
“We need to eat better food, but it is equally clear that regular exercise is also very important in cancer prevention,” said Prof Linda Bauld of Edinburgh University.
Bauld, who is chairing sessions at a virtual conference, Cancer Prevention – Physical Activity, to be held from 23 to 25 February, said that while tobacco and smoking remained the main cause of cancer in the UK, obesity was now the second highest risk and in future is likely to become the main cause.
This is being driven by two factors. More and more people are giving up smoking while rising numbers are becoming overweight and obese – and lockdown has speeded up that process. As a result, it is expected that by 2040 obesity will have overtaken smoking as the leading preventable cause of cancer in women, a pattern that men will follow a few years later.
Among the cancers that have been shown to benefit from improved physical activity are breast and bowel cancers. Those who have been treated for primary tumours have better chances of their cancers not returning if they exercise more often and have improved diets, it has been found.
However, recent research has also highlighted links between exercise and other cancers. In one recent experiment using mice, scientists, funded by Cancer Research UK, compared a group that led sedentary lives with another group that was placed on treadmills for 30 minutes, three times a week. The scientists found gentle exercise reduced the levels of liver inflammation, which can lead to tumours, and improved the metabolism of older mice, even in those that had advanced liver disease.
In addition, the study, which was led by Prof Derek Mann, from the Newcastle University Centre for Cancer, found that exercised mice had less fat in their liver and moved more quickly. “We wanted to see if exercise in mice – crucially, a gentle routine that may mirror exercise achievable for frailer people – could help throw immune decline into reverse and help reduce the risk of liver tumours developing,” said Mann.
The research is important because liver cancer rates in humans have increased by three-fifths in the UK in the last decade, with 17 new cases being diagnosed every day, and rates are projected to continue increasing. “Understanding how to best to prevent some of those cases could have a huge impact for people at risk of the disease,” Mann added.
Another recent study by Cancer Research UK showed that more than 135,000 cases of cancer – about four out of 10 British cases – could be prevented each year largely through lifestyle changes, with increased physical activity of any kind playing a key role.
The crucial point is that extra fat does not just sit quietly around our bodies, say researchers. It is active, sending out signals to other organs and tissue which can affect growth, metabolism and reproductive cycles. These signals can tell cells to divide more often, which can lead to cancer.
“The real problem is having too much fat in our bodies,” added Bauld. “However, there is a lot of evidence that helping people to become more active can do a lot of good. And this area is under-researched so it is very likely that there may be more benefits for cancer prevention through increased physical activity that we don’t know about yet.”
