Filling Bring-to-work lunches

Do y’all have any lunch ideas to bring to work that are actually filling and have enough calories to sustain your appetite? My boyfriend is a type 1, 26 years old, 6’ and ~179lbs. He struggles to find stuff to eat besides a sandwich, and cheap carb options like chips on the side. Then he just snacks on granola bars all afternoon. I’d love to find him something else to bring for lunch that’s both more filling and still nutritious. We don’t think he’s getting enough calories during the day! He works out with weights some days as well. Thanks!