Here are some figures how long eating of some different types of food takes.
In most cases (with exception of gelee royal and food taking 1 turn to eat at least) eating cursed food takes only half the turns it takes to eat an uncursed one and eating blessed one seems to take always exactly same time than eating uncursed one.
So if you need to eat in combat, eating cursed food might be the best idea (for example cursed iron ration gives 250 satiation points in 2 turns which is same what you get from 10 blessed seeds for example).
Code:
cursed uncursed blessed
iron ration 2 4 4
large ration 2 4 4
cooked lizard 2 4 4
corpses* 2 4 4
fortune cookie 1 2 2
stomafillia 4 8 8
other herbs 1 1 1
gnomish candy 4 8 8
gelee royal 8 12 12
seeds 1 1 1
bee wax 1 1 1
*tested with only some basic (uncooked) corpse types, like spiders, bats, kobolds and orcs.