As it turns out, an effective way to keep weight off when you are a student is to adopt a very haughty food snob persona, so that when you are on campus, the various campus dining options turn your stomach so badly that you’re only interested in bringing food you prepared yourself. 

That said, this does require you to have the foresight to create time to bring food from home. It becomes less and less easy to be a food snob when you left the house with only coffee in your stomach.