I think its an honest 50/50 between those who use and those who dont.
There are those that OBVIOUSLY use some form of chemical supplementation. And maybe a few who look like they do but dont.
I also believe that there are some that don't look like they're on gear but do use it. Mainly to elevate their recovery levels.
So even in the case of Bob Sapp... there are genetic freaks.
Very few activities put the kind of strain on your body that this sport does.
You have to dedicate so much time to so many aspects... and very few fighters are able to JUST fight and do nothing else.
Many have to train other people, run a school/small business, perhaps even work another job, do promotions /events for their organization, travel, seminars, take care of a family...
Then they have to train a VAST array of technical skills... have aerobic and anaerobic endurance, be strong and fast...
And now, especially with the fight game gaining popularity in America...
A fighter can't be flabby, they have to be attractive and marketable so your physical appeal plays a great deal into it also (Think wwf/wwe).
So I can buy the "I dont use, I dont even lift weights" argument from someone like Quinton "Rampage" Jackson...
He says he doesn't lift weights (persay) but he is known to carry his training partners around the gym and routinely do clean and press sort of movements with them as part of his workout... Also his physique (while impressive) isn't bodybuilder status. He's lean, but if you've grappled for 2min you would know why. So for him its possible.
Unlike someone such as Phil Baroni or Carlos Newton... I have a HARD time believeing that he's not using. MUCH LESS not lifting weights. Though its entirely possible.
Fedor doesn't count... The T-3000 Doesn't need to use chemicals.
In all seriousness he's someone that I can buy not using. Yet I can also see him using but not in outrageous amounts, just enough to aid in recovery if he uses at all.
Kevin Randleman is one that I believe looks like he uses, but there's a high possibility that he doesn't. Randleman has always looked like that (one big huge ass muscle). He trains with Louie Simmons. He is also a Former Olympic athlete... the man is gifted as FUCK (ie, genetic freak).
But he lifts weights. Would tell you he does...and would advocate it. So he's not exactly hiding anything.
Basically what I'm saying is that you'd be surprised by who uses and who doesn't.
FYI- All that talk about no weights was because the gracies didn't advocate them at the beginning (they lift now though) so just to keep up with the jones guys would say they dont lift weights (but they do).. mind you some truly didn't lift weights but a lot of people just jumped on the bandwagon.