It's not rude, not if you're nice about it. Do everyone there a favor and let him know. Don't be a dick about it, just let him know that it's kinda overwhelming. Hell, leave dude a note if you're scared of him or something.

Just don't be an asshole about it. We all have our blind spots, maybe dude's blind spot is toxic BO? I can virtually guarantee that you have one, so be sure to put yourself in his shoes; wouldn't you want to know? Maybe there's no one in his life that's willing to mention it. Be a hero! Do it!

Aesthetics and sense of smell are pretty much totally learned. "Deodorant" is a petrochemical product that clogs the pores. If you like fake crap more than you like natural smells, you have something wrong with _you_.

Some people have metabolic disorders that no amount of deodorant or showering will cure. He probably knows he stinks. I say just leave him alone.

know where you're coming from...I used to bowl (yes, bowl) in a league where there also was a guy who could 'clear a room' - when it was our teams' night to bowl against his team, we would only be near our lane when it was time for us to throw. Being much younger then, I never did do anything about it, but I definitely would now. (Being much older & sager!)
Their smell could be brought on by a medical condition but after checking I would say that that is highly unlikely - Odds are that this guy just needs to learn some proper personal hygiene. I would recommend that you do have a chat with the gym management, hopefully they can broach the subject with the guy using some sensitivity. Good luck!

Hygiene, petrochemical pollution, all of these things contribute to cognitive decline. The body is a natural ecosystem---it is entirely possible that you are addicted to unnatural smells and are weirded out by nature. I wonder if the OP finds camping "icky" because she cannot shower 5x a day?

I don't think being natural means you need to stink. There are such things as natural soaps and deodorants. I'd report it to management and hope they deal with it. It's in their interest to keep the majority of their clients happy.

Ha. Lots of people stink at the gym. It's called 'really' working out. Fake fucks

Uh, soap is not natural, it's a product of chemistry, albeit primitive. It is not necessary, no other animal uses soap. They may bathe, but they do not use soap. Bathing in water is quite sufficient.

I hope this isn't me. I don't think it is but one really never knows does one? It's like having halitosis, or being too liberal with the cologne or perfume, you get used to it and you are the only one who doesn't realize that you stink. But then again, regardless if your own version of stank, I think everyone is guilty of what Fat Bastard said about farting...everyone likes the smell of their own brand.