The bug
As the player can regenerate health in Creative mode (possibly, to recover from taking damage from the void) hunger is also consumed regenerating this health, which makes no sense as you are not supposed to lose hunger in Creative mode.
How to reproduce
Switch to creative mode and run:
/tp @s ~ -128 ~/tp @s ~ -128 ~Keep flying in the void, switch between y=-128 and y=-129 a few times.
Exit the void and switch to gamemode survival
→ ❌ Your hunger bar has gone down
Is this still an issue in the most recent versions (currently that is 1.10.2, or 16w43a) of Minecraft? If so, please update the affected versions and help us keeping this ticket updated from time to time. If you are the owner/reporter of this ticket, you can modify the affected version(s) yourself.