Changing difficulty from peaceful may cause inaccurate hunger bars on multiplayer servers

The bug

Changing difficulty from peaceful to easy/normal/hard may cause inaccurate hunger bars on multiplayer servers.

How to reproduce

1. You're player A. Create a world and change difficulty to peaceful.
2. Open to LAN and have another player join. They're player B.
3. Change difficulty to normal.
4. Do this command:

   /effect give @a hunger 10 100

Player A's hunger bar will work as intended, but player B's hunger bar will regenerate haunches during and after the effect. This is purely visual, as they will starve to death. Every tick of starvation damage will reset the hunger to its correct value, but it will continue to visually regenerate in-between those damage ticks.