LoseIt: Lose the Fat

Not sure of this fits your Usecase, but bringing some kind of precooked stew to work might fit it. Some sort of lentil stew could work, as you have both protein and fibre. If you need something readymade you can buy at a store, then it could be something highly preprocessed like protein bars and such, which I would nod advise to have in your diet all the time.

Back in the days before "The Incident"(tm) when I was a regular at the office I often had one of those whole-meal-shakes like Plenny/Joylent which covers both protein and fibre and doesn't take much time to make. But tbh: Having a proper meal with colleagues is important and can be good for your psychological well-being. If you are the weird shake-gulper this might work less good. ;)