Actually, if you think about it, they benefit the gym. They come maybe once or twice, but may not cancel their membership for a few months, saying to themselves that they'll "start again next week". When they do come, they're only there for 20 minutes max, and they hardly use the equipment, and despite their size they're usually weak as fuck, and don't really wear the equipment down. So really, fats fuel the gym with more money without using the services enough for the gym to have to replace equipment more as their memberships increase.