I was using the /effect feature with command blocks in order to sustain the instant health effect, which may not be an intended feature. Then, I walked into lava which quickly sapped me of my hunger as I was glitching and shaking rapidly.
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Although crazy behavior, it's intentional that you lose hunger when harmed
CubeTheThird, I used the command /effect @a 6 1000, which extended the time of the instant heal potion to 1000 tics. Thanks for the clarification Jens.
Out of curiosity, were you giving the instant health a long duration, or were you using a clock to repeatedly run the command?