Freshman year changes the spending pattern before it changes the food pattern. Weeknight meals are already covered by the meal plan, so those calories tend to average out on their own. Weekends work differently: cover charges, drinks, and whatever gets ordered afterward are all separate decisions, usually made close to midnight, usually in a group.
The weekend spending shift
A night out easily adds several hundred calories in drinks before any food enters the picture, and the number climbs faster once refills and mixers are counted instead of guessed at. None of that shows up on a dining hall tray, so it is easy to lose track of.
What happens after is the bigger shift. Nobody wants to cook at midnight, so it becomes pizza, fried chicken, or a drive-through order split between roommates - and because the bill is split, portions stop being tracked at all. That order is often the single largest meal of the week, eaten the fastest, with the least attention paid to it.
Eat before you go, not after you're back
One change that does not touch the social side of the weekend at all: eat something before heading out instead of after getting back. A handful of dried dates with a glass of water covers the gap between dinner and whenever the night actually starts, so the 1am food decision gets made from "I feel like it" rather than "I haven't eaten anything in six hours." Medjool works for this if that's what's in the pantry, or whatever grade is on hand.
The day after matters as much as the night does. Skipping breakfast to "make up for" a heavy weekend does not undo anything - it just adds a second gap that gets filled later, usually with something worse. Keeping Sunday and Monday on a normal meal schedule is what actually breaks the pattern, not skipping the next meal out of guilt.
None of this means giving up going out. It means treating weekend food as food, not as an afterthought squeezed in between a night out and sleep. Dried and fresh dates both keep well in a dorm room without refrigeration, which is most of why they work for this better than anything that needs prep.