After playing in creative for a while I decide to switch to Survival. My game difficulty is set to Easy. The first thing I notice is the stamina/hunger bar is empty. The second thing I notice is I start losing heath because I am starving to death. I believe when playing in creative the hunger bar over time is used up in the background.

Steps to duplicate
-Make a creative world.
-Make sure your game difficulty is on Easy
-Run around for 15 minutes in creative. (Sprinting)
-Switch to Survival.
-You will notice that hunger is being used during the time you were in creative.