I heard the Messenger of Allah ﷺ say: "A human being fills no worse vessel than his stomach. It is sufficient for a human being to eat a few mouthfuls to keep his spine straight. But if he must (fill it), then one third of food, one third for drink and one third for air."
عَنِ النَّبِيِّ ﷺ قَالَ «مَا مَلَأَ آدَمِيٌّ وِعَاءً شَرًّا مِنْ بَطْنٍ حَسْبُ ابْنِ آدَمَ لُقْمَاتٌ يُقِمْنَ صُلْبَهُ فَإِنْ غَلَبَتْهُ نَفْسُهُ فَثُلُثٌ طَعَامٌ وَثُلُثٌ شَرَابٌ وَثُلُثٌ لِلنَّفَسِ»