Only on Lemmy would someone with (likely) zero experience in combat sports tell someone that a sport known for rampant knee issues is “their fault”, and not due to the increased force on the knees from doing a ground-based sport.
Again, only on Lemmy would someone say “you can’t be fat in your seventies, these famous people aren’t”.
That ignores a huge psychological aspect of weight gain, alongside several questions that contribute:
I can say that for the latter points, it is incredibly hard to do so, looking at my parents and with people I’ve trained with. Furthermore, going from fighting fit to limited care can make you explode in both weight and joint issues. I’ve trained with a few army guys or people with pro sports experience, and it’s mad how even in your forties you can go from a sub-twenty minute 5k to throwing up on a mat during a 5 min spar.