Bodybuilding is also the only one that I don't really consider a "sport." It's a beauty contest. I think the prevalence of fads is higher because there's no objective performance metric.
While I share your suspicion that anything requiring judges to give a score is probably not a sport, if there's one thing bodybuilders and "fitness" models are masters at, it's manipulating water retention. They've got it down to a dangerously scary fine art.
... on the not-so-glorious side of the ledger, they probably know more about steroids than anyone short of an ex-East German sports scientist.
Actually, I think wrestlers may be just as good at manipulating water weight. The biggest difference being that wrestler have to compete soon after, and if they didn't cut properly, they'll become exhausted during their match and get mauled.
