I'm 57 and I bike 25 or 50 miles four days out of every five, and I work out at the gym every day. I had stretches when I was a decade or two younger where I did nothing but eat and smoke pot and I weighed forty to fifty pounds more than I do now; during those stretches I felt like I was 80 and hurt all over all the time. Sometimes older folks have severe injuries that prevent them from doing anything physical and the decay just adds up, but for a lot of people being sedentary creates the illusion that aging is unstoppable. Of course it is unstoppable ultimately, but you can sure as fuck do a lot to slow it down.