I was, and still am, the other way around. Proportionally, I'm built as if you're looking up at me. Super long legs, a torso too small to hold on all my internal organs without a belly popping out (even when I was scrawny, I had a gut) and a wee itty bitty head. (To make it truly Surly: The only gal I was able to comfortably 69 was under 5 feet tall. Everyone else was too long.)
Not only was I skinny, I was small for my age up until high school, where my legs finally pushed the rest of me up to average height.
Even in undergrad, me and my gang would head out to the County Line and order all you can eat. They were 240, 260, and 280 lbs; I was (as mentioned) 125. One night we each ate a full platter each. I was eating as much as they were... couldn't gain weight. Just a stupid fast metabolism that wouldn't let me gain fat NOR muscle until my mid 20s.
I never had trouble hitting people and my love of the mosh pit proves that. But I would've died on a high school football field.