This bug is VERY old and unnoticed, since sprinting and the hunger bar were added, this bug is present: when the autojump setting is on and the player goes up on stairs, the autojump acts repeatedly in a REALLY short amount of time, this leads to a drain in the hunger bar, it can drain a whole bar in just 50 SECONDS or even less.
I don't know if this bug is present on the Java Edition as well.
Thank you for your report!
We're actually already tracking this issue under MCPE-64793 so I've requested this report be resolved and linked as a duplicate.
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