How do I weld a mesh to a character/player?

This may sound confusing at first but, I'm making a game called Diet Simulator where you can either get fat or get stronger. So he question I have is how do I create fat. If you check out B-b Studios Eating Simulator, you'll see that when you eat your stomach gets bigger. That's what I'm trying to do. So basically when you eat and gain "Fat", you grow taller and wider. But I also want it so your stomach grows bigger too.

Anyone know how to do this? I believe it has to do with a weld script, but I don't know how to make a weld script that connects a part to a player? Anyone have a script for that?