great to see, that you are interested in sportsclimbing, and thx @Fremen
for the tag. I am happy to share my experience.
During 30years of climbing I have seen multiple big (bodybuilder or obese does not realy matter here) people climb and I have also belayed heavy people during the time I worked at the climbing gym.
So, the most importantly: In general, it is possible. Everyone can (and should 😉) climb.
But there are various aspects to be aware of:
How does the belaying work: human belayer or belaying machine?
Both have to be capable to hold your weight... Just call the gym, I am sure there will be someone, who can give you the information.
Back in the days, I was one of the heavier guys in the team, so I was called, when there was a heavier person to be belayed (>220lbs).
As a well trained belayer with my ~180-200lbs I am/was capable of belaying a person up to 300lbs in a toprope situation with an extra weight attached to my harness. So if you book someone who does the belaying, tell the them in front and be honest with your weight, so the staff can get someone who is capable of belaying you.
The harness needs to fit around your belly. Again, ask at the gym. I never had a non-fitting one during my years working at the gym.
My advice: Don't let a beginner belay you, if the one is not at the same weight level as you are.
What are you capable of: it depends.
- the easy routes are usually set to use your feet a lot and the hands are used to hold your weight over your feet. If the wall is vertical your body is already in an overhanging position (what @Froud
(Don't train hanging, it puts a lot of pressure on your arms/hands etc. The risk of an injury is not worth the benefits.)
- if the angle of the wall is like a little ramp (opposite of overhanging) it is even easier. But those walls are a lot less common. Ask your friends, how the easy routes are set in that particular gym.
In the end you have to try yourself, what works for you and what doesn't. Don't be ashamed if you can't top a route, the goal of a beginner is to climb... Even if you do the first 10 feet multiple times. Just climb, try, "fail", try again, try other routes, fail and so on.... And have fun!