I would have thought that the standard of fitness among aircrew would be very high anyway, to handle high G and also in case of E & E. It's in their interest to be very fit and healthy.
Unfortunatley there will always be a few fat scranbag's hanging around the station and they need to be beasted. Mind you if they can get their podgy little fingers around their spanners or stacking blankets then is there a problem?
It's always handy to go on the pull with a chubby in tow anyway, atleast your garunteed the lookers.