When I came to the University at the beginning of September I noticed a lot of differences between my high school's cafeteria and the residential dining hall. There were a lot more options at the dining hall and you could go back and get food as many times as you wanted.
From a health and portion perspective neither of these things are necessarily good. With so many options, it's hard to decide and you often want to try more than you are really hungry for. Since you can go up multiple times and get food, you may eat more than you think you are.
One other big change from high school cafeterias is that the dining halls do not have trays. This is not by accident. Not only is it less dishes to wash, but the absence of trays is supposed to combat the issues mentioned in the previous paragraph. Without trays you can't have multiple plates; you can carry one plate and your drink. This is supposed to encourage diners to decide on one dish. This article points out people will be less likely to go up for seconds because they have to make a conscious decision to go get more food.
I don't know if I agree with all of their reasoning. Sanford dining hall is tray-less and people seem to have no problem juggling multiple plates or setting their plate down and getting more. I think it's a hassle to not have trays because if you are trying to carry your plate, silverware, and drink and then you decide you would like to grab a bowl of soup you either make multiple trips to your table or balance really well.