I had another go at reproducing the double-food bug and I think I found the cause:
I have a save with 14 food and I tried loading it, eating all the food, quitting and reloading and repeating. It seemed really inconsistent at first, sometimes happening and sometimes not, but I think I found a way that causes the bug almost every time. I think it has to do with whether the mouse has moved between clicks!
1. Have at least 10 food so you have enough to try a few times.
2. Move the mouse over the food item in the inventory.
3. Lift your mouse off the table so you can't move it at all.
4. Left click to select food.
5. Right click to eat food. It will probably eat only 1.
6. Right click again to eat food, it should eat 2-3.
This never seems to happen if the mouse has moved in between steps 5 and 6.
Hope that helps