Healthy lifestyle while in school

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Hey guys,
I'm looking for some advice on what small changes or things I can do to keep healthy in school (besides taking the stairs, I already do that).

The stress of work and school has take a toll on my body physically as well as mentally and I'm looking to try to lose a small amount of weight and feel better in my body without stressing myself out too much.
Unfortunately my schedule is super tight so I can't make it to the gym as much as I'd like to but I'm trying to go at least twice a week.

Any advice would be super appreciated, thank you !!