People who are thin and angular tend to have higher metabolisms. That's because a larger percentage of their body is surface area, which dissipates heat. Their bodies have to release more energy in order to maintain their internal temperature. Such people can consume prodigious amounts of food without gaining weight; indeed, they probably require it.
I used to work with a guy who was about 6 feet four inches tall, 35 years old, and skinny as a rail, though he was muscular and built sturdily. On a typical afternoon this guy would down a dozen bakery doughnuts; one right after the other, then pull out a 1 pound bag of M&M's almond candies and put the entire thing away. He never gained weight, but always complained of being cold.
That guy sounds like me. I am 6'2 and weigh 207 lbs. But my sophomore in high school i weighed 155lbs. I had to go on an eat all I could see diet as well as lift weights to get to where I am at now. If I take 2 weeks of off eating and training my weight tends to go right back down to 200lbs. Heck I took the whole summer off of lifting weights and eating 6 times a day and my weight dropped from 204lbs to 192lbs.