gut-busting
1. Very difficult or tiring. Boy, moving all that furniture was gut-busting work—I'm exhausted. I'm not looking for some gut-busting workout, so I think I'm just going to take a gentle yoga class.
2. Focused on reducing the size of one's stomach (or "gut"). I definitely need some gut-busting exercises before bikini season rolls around.
3. Describing food that is in some way very unhealthy. You can always count on Aunt Mary to bring some cheesy, buttery, basically gut-busting, casserole to Thanksgiving dinner.