August 9, 2016

expert reaction to study looking at weekly activity levels and five chronic diseases (breast cancer, bowel cancer, diabetes, heart disease and stroke)

A group of researchers publishing in The BMJ have examined the effect of physical activity on breast cancer, bowel cancer, diabetes, heart disease and stroke and report that people who significantly exceeded current minimum levels of exercise had a lower risk of those five diseases.

Dr Oliver Monfredi, NIHR Clinical Lecturer in Cardiovascular Medicine, University of Manchester, said:

“This is an important and well performed piece of research, looking at the complex issue of the protective effect of exercise on several common illnesses that are highly relevant in British society today.

“The study aggregates the results of a great many other studies, to give an idea of the overall effect. It includes only studies that set out to prospectively monitor amounts of exercise performed, which is a more accurate way of quantifying actual exercise undertaken by individuals, rather than other studies where participants are asked to recall the amounts of exercise performed over many months or years, which is prone to error.

“The study demonstrates that exercise has a protective effect on the development of all of the studied illnesses. It suggests that more exercise is better, but that the benefit is felt most keenly by those going from very little exercise to mild to moderate amounts of exercise, and that while there is additive benefit in doing more and more exercise, the relative benefit drops off – there are diminishing returns from performing more and more exercise in terms of the protective effect versus the five studied conditions.

“The most beneficial level of exercise differs in all of the conditions, meaning that it is not possible to give a level of exercise that is the panacea for all conditions. We also know from other recent research that at some stage it will be likely that the beneficial effects will plateau, and thereafter performing more exercise may become detrimental to health.

“The study makes important insights into the limitations of using the MET as a way of quantifying exercise exposure, with its failure to reflect differences in exercise intensity undertaken, and whether this is predominantly aerobic or anaerobic.

“What is clear, in summary, is that in terms of protecting oneself from the development of these five common and potentially life limiting illnesses, undertaking any level of exercise is protective, more is better, and should be encouraged by health care professionals, politicians and charities alike, to decrease the burden of these debilitating illnesses in society today.”

‘Physical activity and risk of breast cancer, colon cancer, diabetes, ischemic heart disease, and ischemic stroke events: systematic review and dose-response meta-analysis for the Global Burden of Disease Study 2013’ by Hmwe H Kyu et al. published in the BMJ on Tuesday 9 August 2016. 

Declared interests

Dr Oliver Monfredi: “I am employed by the University of Manchester.  I receive grant funding from the British Heart Foundation.  I am a special volunteer at the National Institutes of Health.”