Alien Sim Suddenly Skinny

Hello,

I've been playing with a different family and while doing so I met one of my sims, hanging around and being extremely skinny. So I changed household to that sim to see what was going on and after I entered CAS full mode and the sliders are greyed out, so I can't do anything about his disguise (he is an alien)

He was quite musclar and I'd lik ehim to go back to that.

I don't use mods not cc. 

Help?

ToKi