Were you on a bow bar with active poisons? I've been seeing reports that food doesn't work right when refreshed on a bar like that and tested it last night. While on my bow bar, after refreshing tri-stat food, I was about 1k shy of normal health numbers. I swapped bars and re-ate the food and it was normal. Not sure if all poisons do this, I was using the junk cloudy ones that drop in game.