I did a little research on food and hunger.
The hunger meter regenerates health when it's above 80%. All foods take 1.6 seconds to eat and only heal by refilling the hunger meter EXCEPT
(1) Cakes, which are instant-feed. They still have to be placed before being eaten and they can't be picked back up, but you don't have to go through the feeding animation TO eat them. Each bite gives you back 10% of your hunger meter.
(2) Golden apples. Golden apples give you back 50% of your hunger meter and they give you a temporarily "boosted" heal rate, even when your hunger meter isn't high enough. It boosts health for about 25-27 seconds, with 22 seconds being long enough to regen back to full health from a half heart (so you can actually eat a golden apple, get attacked, and still end up with full health after you're done regenerating). I haven't tested if healing is even faster if you have more than 80% on your hunger meter, but honestly, it's still pretty quick as-is.
SW-5120-1900-6153
