The gut microbes in rats also seem to benefit from voluntary running on a wheel. Researchers have found that the exercise also seems to lead to higher levels of a particular short-chain fatty acid called butyrate, which is produced by bacteria in the gut through the fermentation of fibre and has been linked to numerous health benefits. Butyrate itself plays a number of roles in the body – it is the primary fuel for our gut cells, helps to control the gut barrier function and regulates inflammation and the immune cells within our gut.