I have never asked, but ... no. But you could get a sandwich and such to "take back to your room'" and if it accidentally falls into your shore excursion bag, well, have the common sense not to eat within view of the ship.
Actually, I eat before I go, and eat when I get back, because there is always food being served on board. Or - it won't bankrupt you to support the local economy and eat on shore. {try for something local - like seafood, or their fresh fruit smoothies, or whatever, for a nice change of pace.}
Where's the nearest Starbuck's??!!
Edit: Some long excursions will provide lunch, so read the itinerary closely.