im guessing when you say "brothers" you are talking about the brotherhood of firefighters. I wouldnt be to quick to put down firefighters because of your own bad experience (people are what they are regardless of the job). It is a high stress job and it has certain stereotypes that can make it hard for a gay firefighter to feel comfortable coming out. But thats a different story since this topic is about overweight/obese firefighters. Ofcourse there are overweight firefighters, but there are fitness requirements and if they dont work behind a desk then they must meet those in order to work. they are placed on light duty if they cant meet the fitness requirements, that usually shakes them up in to losing a few pounds. The biggest problem that faces firefighters is food, which is in its self based on personal decisions.
But to restore your faith, alot of firefighters are in shape. check out their calenders or google their company sport teams. my dads station for example is big on rugby and soccer.