“And eat and drink but waste not by extravagance, certainly He (Allâh) likes not Al-Musrifûn (those who waste by extravagance)”
[Sûrah al-A`râf: 7:31]
Extravagance leads overstepping the mark, which means eating beyond the point of fullness. This is not limited to one or two or three meals a day. A person may eat one meal a day and eat extravagantly during that meal. Or he may eat three meals without being extravagant.
He Prophet (peace be upon him) said: “The child of Adam fills no vessel worse than his stomach. Sufficient for the child of Adam are a few morsels to keep his back straight. If he must eat more, then a third should be for his food, a third for his drink, and a third left for air.”
[Sunan al-Tirmidhî (2380) and Musnad Ahmad (17186) and authenticated by al-Albânî in Sahîh al-Jâmi`]