Exercise & Breast Cancer

Found this post from when I was working on this. It is a brilliant example of how complex  cancer is and I hope it stands to prove the over simplification at best and extremely dangerous at worst of claims like ‘ketones can help your cancer’..

Exercise and breast cancer: the effect on the tumor

This data is from animal models of breast cancer expressing triple negative tumors which are the most aggressive, hardest to treat and have the poorest outcomes. 

Before anyone says ‘it isn’t relevant because we are not mice’ .. yes there are limitations however;

– Animal models provide a tool to examine the effects of exercise on tumors in a closed experimental environment in which the lifestyle of the animal as well as the type and intensity of exercise can be controlled. This is not possible in the real world.

– Individuals with breast cancer display huge heterogeneity (they are all different) not just in terms of individual differences in health, age and ethnicity but in relation to their breast cancer type and treatment. This is less of an issue in genetically engineered mice models.

– Animal models also allow us to watch the tumors grow and thus make possible the detailed study of stage-specific responses to exercise. This gives us a greater insight into the development of tumors in relation to exercise and may help to identify the optimal mode, intensity and duration of exercise. 

In conclusion, some of the huge limitations in exercise science – namely sample size, heterogeneity of populations and lack of control can be overcome using animal models. We need to piece the information we get from human and animal studies together to give us the most comprehensive understanding.

On to what animal models can show us about the effect of exercise on breast cancer tumors..

– A reduction in tumor progression. Both the number of tumors and the size of tumors were reduced with exercise. 

– This reduction is thought to be linked to a reduction in inflammation (MCP-1 and IL-6 were both reduced)

– Intensity matters! – the reduction in tumor progression is generally seen in studies that have opted for exercise intensities of about 70% VO2 max. Interestingly, studies that have opted for low intensity exercise have found varying results with some even showing an increase in tumor progression. 

– The age of initiation of exercise (probably in relation to tumor status) may be of importance. Two very similar studies were carried out on a genetic mouse model where one study found a positive effect of exercise and the other found a slight negative effect. One of the key differences is that the positive effect was found when mice began exercise at a much younger age and the negative effect was observed when mice began exercising later in life. This may have implications for the age at which we encourage girls to start routinely exercising.


This last point especially shows the complexity of cancer and how all tumors act differently & actually how even the same tutor can respond differently to a stimulus at a different stage in its life.