People who usually eats a lot without gaining wait has fast metabolism. Actually, I am jealous at those people because I usually gain weight when eating a lot that's why I am controlling my food intake as I am overweight. I knew a lot of people who are either male or female who eats a lot. They even eat two to three cups of rice in one meal. They eat a lot of meat than vegetables . They eat a lot of junk foods. Though they are not gaining weight. I hope I can be just like them.
A fast metabolism. You can check your poop for anomalies but you need to go to the doctor to see if it is not a problem somewhere. It could be a worm or a lot of other thing. Not to scare you or anything it's still normal to have a fast processing Metaboliusm.