Is there a way to get more variety in the body types for Sims 2? The game’s version of “overweight” is really just a little pudgy. And there is no “skinny,” just normal. I mean really… creating a greasy, dirty Bubba just isn’t the same when he only has a little potbelly… 
I -think- you can make your Sim fatter or fitter during the game, depending on the kind of lifestyle you lead. You can definitely make them more fit by regulating how much they eat and exercise. I’ve never tried to make them obese, though. It’s worth a shot, I guess.
This is something I’ve wanted added since the game came out. “Thin” is just kinda ordinary-slim, “fit” is a little bit toned, and “fat” is a just kinda pudgy.
I always thought there should be three extra, more extreme, body types: skinny, pumped and obese. Working out how one type transitions to another might be tricky, but it seems doable.
There’s nothing in the game, but you can download user-created bodies to diversify your Sims’ world. They won’t appear as options in Bodyshop, but they’re tied to clothing. Mod the Sims 2 is a good place to look. You’ll have to register to download the files, but that’s no hassle. They have an entire section dedicated to it – Body Types. There’s one woman who does really great curvy woman bodies, ones that I think match my body type better than the ones available in the game. Unfortunately, I can’t remember her name. There are also bodybuilder types, but I’ve never looked for potbellies or anything, so I can’t tell you on that. Sorry!
I will warn you, though, that you read the descriptions carefully. This won’t be an issue with MtS2, since they have a separate site for adult content, but if you don’t want Sims walking around with inappropriately sized sexual organs, then read the fine print. It’s usually pretty obvious, but sometimes . . . it’s not.