Couch potatoes have smaller brains later in life: poor physical fitness in middle age may be linked to a smaller brain size 20 years later https://www.aan.com/PressRoom/Home/PressRelease/1432 Gut starts ageing at 55: levels of friendly bacteria in the gut drop significantly after 55, particularly in the large intestine. Sport: 20-40% Reduced Cancer Risk with Regular Exercise http://fitness.mercola.com/sites/fitness/archive/2015/04/10/exercise-cancer-dementia.aspx