fast acting food

Any snack or meal that passes through you so fast (think "bad poopy"), that it is almost as if you hadn't even eaten.

Wow, that was some fast acting food ! I didn't even get out of the Chinese restaruant before it left my system.

Dudette, what was up with that chocolate cake at Carissa's last night? It was like, wicked fast acting food! I bet I didn't gain an ounce but I don't think I want any more anytime soon.