Moreso I'm worried about the procedure itself, the pain and recovery involved, and whether I'll experience other physical changes, like weight gain, decreased activity level, penile discomfort, etc.

Well, no.

Actually, I take that back. If you sleep on your stomach, trying to get your dick adjusted right the first couple nights afterward is indeed uncomfortable. Especially if you're sleeping in the dick sling. In fact, the whole athletic supporter experience is just a pain in the... well, dick. Not pain, but annoying, really.

In fact, that's the most I can say about the entire experience. I never felt a bit of pain after the initial numbing shot. Discomfort, annoyance, aching, yes. But pain... nope. Nothing that couldn't be quieted with two old fashioned aspirin.

As for the rest... there's nothing about a vasectomy that would cause weight gain or decreased activity level or anything like that. It's just some plumbing being rewired and capped off. No hormones are being affected or anything like that. You probably won't be able to work out for a week, but that's about it.