I have a skinny little guy in my daycare who can east 2nds, 3rds, 4ths, but I usually cut him off after 2nds or 3rds. I'm not sure he can tell when he is full. His parents are both very large people and I think he is used to larger portions at home than he is at daycare. But when I put the children's plates in front of them they have a lot of food on there and one serving is enough or too much for the other 4 children. I guess some children must have really high metabolism.