Athletes consume a huge amount of calories in their playing days. When they retire, their brain is probably still expecting all those calories, so it’s probably very difficult for them to stop consuming while they stop all the exercise, leading to even more fat gains while losing muscle. Plus with the PEDs they stress the organs, particularly heart. And then there is the constant partying in the days of fame and fortune, including loss of plenty of sleep.
it’s not surprising many athletes did young.