Note: This is also reported on Java Edition at MC-237429.
There is a texture in the game's files called hunger_blink. The texture should be used to indicate either when the hunger bar empties or gets restored, similar to the heart one when the player takes damage, which makes the heart turn white, however, the hunger counterpart seems to be unused and never appears in-game. the texture can be located at the vanilla resource pack/textures/ui and at gui/icons.png as well.

Stepts to replicate

1. Restore any hunger or make the bar go down
2. Notice no flashing
3. Make the healt bar go down
4. Notice flashing.

Observed

When the player loses/gets hunger, the hunger bar does not flash, unlike the health bar. When the player takes damage or regenerate, the health bar does flash with the use of a similar texture from the hunger_blink one; however, the heart variant almost does not appear because of MCPE-33658.

Expected

The hunger bar should flash with a white overlay every time the player loses or gets hunger, like the healt bar does.