I work overnight but my job is super physical and I have chronic stomach issues so I keep losing without trying (which is also becoming problematic).

Have a big meal before work and try to eat lightly throughout the night. Then, have a small meal or a few snacks when you get home to satiate you before bed. I've read that eating a lot during night shifts can mess with your blood sugar and stuff. High protein foods will keep you fuller longer. Avoid drinks other than your basic coffee or water, because things like juice can be hella sugary. If you need easy, healthy snacks to reach for try cheese & grapes, bananas, protein bars, raisins and nuts, applesauce, etc.

If you don't have time for big workouts, try doing a bit of tabata or hiit interval training either before work or after to tire yourself out before bed. Fitness Blender has a boatload of free workouts that require little to no equipment, and they offer modifications/alternatives to exercises for various fitness levels and abilities. Even a little bit of floor pilates or yoga will still burn calories, and help with strength and flexibility.

If you work at a desk you could try and get one of those little foot pedal thingies.

Hopefully at least a smidge of that was useful lol.