The bug

The icons.png file contains the following four unused textures for the hunger bar: a lighter version of the full and half icon, as well as Hunger effect variants on both. These presumably are intended to be used when the hunger bar decrements, in an analogous way to taking damage causing hearts to flash. However, this does not happen, and the hunger bar just decrements quietly instead.

This ticket concerns the center region of the hunger icon - the outline flashing is reported separately under MC-237429 as it appears in slightly different circumstances.

How to reproduce

1. Cause the player's health to decrement by taking damage
   1. Note that the center of the heart flashes brighter to highlight the lost amount of hearts
2. Now cause the player's hunger to decrement through applicable activities
   1. Note how there is no flashing center region for the hunger bar in this case

Other thoughts

As stated before, splitting icons.png into multiple sprites is something I'd recommend and would probably help stop unused icons from accumulating in future.