Minecraft wiki entry for Beginner%27s_guide, associated text: The primary drain on hunger is from healing damage, and for quite some time, eating is your only way to heal damage! Fighting (even before healing damage), sprinting, and jumping are also energy-intensive. (Be careful about going uphill with auto-jump!) You have a little grace period (see "saturation") when starting the game and after eating, but when that's exhausted, your food bar starts rippling. At this point, healing damage, or getting too athletic, starts to drain your hunger bar.