a couple of pounds since coming to college. He has never had a weight problem. He was always active every day in high school sports. Alan admits that his eating habits probably aren't as good as they should be. Still, he eats only three meals a day and a snack at night. He doesn't snack between meals because he doesn't get hungry. The food servers in the cafeteria where he eats always give him generous servings of food. Alan isn't involved with any college sport, but he does play basketball with his friends occasionally. He also has a part-time job and has a full course load. Alan thinks he is more active in college than when he was in high school. In fact, he often feels rushed going to classes because of the distance between classroom buildings and the fact that most of his classes are on the third or fourth floor and he has to wait to get an elevator. The most likely cause of Alan's weight gain is