I did some research on body types. I'll try to explain my findings below.
Here are my two favourite animals. Cookie the mongrel is what we call the ectomorph. Characterized by smalls bones and very little muscle mass, ectomorphs are generally lean and mean but have a hard time packing on the muscle. Cookie is a picky eater who eats slowly with finesse, hence he's too skinny. He'll make a good fashion model in our world of homosapiens.
Rusty, on the other hand, is the mesomorph who has the tendency to be muscular and ripped. A mesomorph can generally build muscle and shed away fat with considerable ease. Rusty is the greedy one who gobbles up everything edible in sight, except dried dog food. If he were a man, he would have a body that'll make girls swoon.
I am probably the endomorph ... generally what most people consider “stocky” creatures, many of them having short but thick limbs and heavy bones. (ok, ok, I am not stocky, only I have heavy bones) Many endomorphs desire a leaner, more defined look, (absolutely!) and should try cutting the fats down to a minimum. Cardiovascular regimens – anything from swimming to biking – is essential for endomorphs looking to trim down. (yikes!) Thirty minutes per day, four days a week, will keep the jelly out of the belly. (you bet!) Meanwhile, weight training should contain sets of several repetitions at a moderate weight, with limited time spent between sets. (must I really do all that?)