Abu Karima al-Miqdam ibn Ma'dikarib said, "I heard the Messenger of Allah, may Allah bless him and grant him peace, say, "A human being fills up no vessel worse than his belly. Enough for a son of Adam are some morsels which will kept his back straight. If it cannot be avoided, then a third is for his food, a third for his drink, and a third for himself."

Riyadh-as-Saliheen by Imam Al-Nawawi, volume 4, hadith number 516 - Sunni Hadith