What do you consider "in shape," or your ideal body type. While there are of course many exceptions to who does what Muay Thai and BJJ build your body in entirely different ways...
Muay Thai tends to favor taller lankier individuals and develops thin ripped bodies and lots of speed. Think Brad Pitt (Tyler Durden) in fight club.
BJJ doesn't develop behemoths, but it does generate a more thick build with way more work in the extremeties (arms, wrists). Look up some pictures of guys whose last name is Gracie.
For another alternative workout option try rock climbing...
