A new study has established – in real numbers – that cardio fitness significantly lowers the risk of developing colorectal and lung cancers.

It also found that people who developed these cancers, and were otherwise fit, were less likely to die than people with low fitness levels.

The study, headed by Dr Catherine Handy Marshall, from the John Hopkins School of Medicine, investigated 49,143 adults who underwent exercise stress testing from 1991 to 2009 and were followed for a median of 7.7 years.

Participants in the highest fitness category had a 77 per cent decreased risk of developing lung cancer and a 61 per cent decreased risk of developing colorectal cancer.

Much higher chance of cancer survival linked to fitness

Among those who developed lung cancer, those with the highest fitness had a 44 per cent decreased risk of dying following treatment.

Among adults who developed colorectal cancer, those with the highest fitness had an 89 per cent decreased risk.

“Our findings are one of the first, largest, and most diverse cohorts to look at the impact of fitness on cancer outcomes,” said Dr. Handy Marshall in a prepared statement.

Fitness testing is commonly done to establish heart problems and tolerance for exercise.

Stress-test patients urged to ask about cancer risk

Dr Handy Marshall advises that when people undergo a stress test – or already have done so – they could be informed “about the association of fitness with cancer risk in addition to what fitness levels mean for other conditions, like heart disease.”

Dr Handy Marshall noted that the benefits of exercise and fitness were on a sliding scale. People of moderate fitness still gained benefit in terms of lower risk and great chance of cancer survival. While those of poor fitness were at greatest risk.

While the study confirms an association between fitness and cancer risk, the precise mechanism is yet to be determined. But some of the answer is to be found in people who lack fitness – and tend to be overweight or obese, and burdened with unhealthy insulin levels, inflammation and compromised immunity.

All these conditions are known risk factors for cancer and other diseases. And the John Hopkins research is supported by previous research.

Previous research support the new findings

In 2015, scientists from the University of Vermont found that high cardiorespiratory fitness (CRF) in midlife was associated with a 55 per cent lower risk of lung cancer and a 44 per cent lower risk of colorectal cancer compared to men with low CRF.

The study also found that high CRF in midlife was associated with a 32 per cent lower risk for cancer death among men who developed lung, colorectal or prostate cancer.

Cardiorespiratory fitness levels were assessed between 1971 and 2009, and incident lung, prostate, and colorectal cancer were divined using Medicare claims data from 1999 to 2009; the analysis was conducted in 2014.

Oddly, the study found that higher cardio fitness was associated with a slightly higher risk of prostate cancer.

The researchers suggested this may have been because of a higher incidence of screening at the GP level.

In 2016, researchers from the US National Cancer Institute investigated the association between cardio fitness and a raft of cancers by pooling the results of 12 large studies conducted both in the United States and Europe, including over 1.4 million people.

Study participants provided information on their lifestyle, including physical activity. All of the illnesses they developed were recorded, including nearly 190,000 cases of cancer.

The research team compared the rates of cancer in those people with the highest levels of physical activity and those with the lowest levels.

They found that those with the highest levels of physical activity had lower rates of cancer of the oesophagus, lung, kidney, colon, head and neck, rectum, bladder, and breast, as well as of two cancers of the blood, myeloma and myeloid leukaemia.

The rates of these cancers in the most active people were seven per cent to 38 per cent lower than in the least active people.

Again, the most active men had a higher rate – in this instance, four per cent – of prostate cancer. It also found a 28 per cent higher rate of melanoma in fitter people.

Researchers suggested might be because fit people spend more time in the sun.