Miqdam bin Ma’dikarib (may Allah be pleased with him) reports: I heard the Messenger of Allah (peace and blessings be upon him) say:“No man fills a vessel worse than his stomach. It is sufficient for a person to eat a few mouthfuls to keep his back straight. But if he must (eat more), then one third (of his stomach) should be for food, one third for drink, and one third for air.”Sahih, narrated by al-Tirmidhi and Ibn Majah.