after eating hunger bar will randomly lose 1.5 points of hunger

i exspected was while i was standing still i could regain my health after eating

what happened was after i ate i gained 2 hearts back before my hunger bar (while standing still and not preforming any actions) lost 1.5 points
of hunger
1. play on amplified world, normal difficulty, no cheats or loot boxes
2. bring hunger down
3. eat food (it happened most with Bread)
4. stand sill and hunger should drop by .5 then 1.0