We always hear the 2nd part of the hadith, but actually the whole idea of the hadith is as follows :
On the authority of Al-Miqdaam ibn Maadiy-Karib who said: I heard the Messenger of Allah saying:
"No human ever filled a vessel worse than the stomach. Sufficient for any son of Adam are some morsels to keep his back straight.
But if it must be, then one third for his food, one third for his drink and one third for his breath."
Ahmad, At-Tirmidhi, An-Nasaa’I, Ibn Majah – Hadith sahih.
Muslim restaurants or stalls should offer 'sunnah portions' :D (if they don't then we can ask for less)
We are [I am] ALWAYS eating too much.