> each hour you spend exercising extends your life by around 3.5 hours [...] They say 2.5 hours per week over a 75 year lifetime makes you live 3.5 years longer

> each hour you spend exercising extends your life by around 3.5 hours [...] They say 2.5 hours per week over a 75 year lifetime makes you live 3.5 years longer, and 2.5 hours per week over 75 years is around 1 year. That is significantly overstated. The study did not establish causation, only associations. The most that can be claimed is that A was predictor of B for group C.