Replenishing hunger glitch

basically i locked my difficulty as normal. then i went through a nether portal and pressed escape i noticed that i was now able to change the difficulty. So with couriosity i changed it to peaceful to see if it would work... although it did not get rid of the mobs around me my hunger started to replenish . so to try and find the full extent of the glitch i started to run around the nethermy hunger started to increase i kept running until there was only 3 hunger bars left and stopped when suddenly my hunger started to replenish. so i believe this is a game breaking glitch!