Sunan Ibn Majah 3349: Miqdam bin Madikarib said: “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.’”
Sahih al-Bukhari 2651: ...The Prophet (ﷺ) added, 'There will be some people after you, who will be dishonest and will not be trustworthy and will give witness (evidences) without being asked to give witness, and will vow but will not fulfill their vows, and obesity will appear among them."