There is an assumption here that there is something wrong with being fat. But Fat Paul's size is an asset (possibly his greatest asset).
He was much in demand when they were choosing people for the tug'o'war team.
It's a long time since I read any 'Big Fat Rosie' stories, but I seem to remember that she used her size to advantage.
It would be wrong to criticise people or make fun of them for something they have no control over, such as their height or colour, or a disability - or do we have to call it a 'challenge' - but if they decide to eat too much (in your opinion) or exercise too little (by your standards) then that is their choice.