Eating only for pleasure and enjoyment
A Muslim should not intend mere pleasure and enjoyment when eating. Allah has condemned the unbelievers for their eating out of pleasure and enjoyment, "Those who disbelieve frolic in pleasures and eat like cattle eat. The fire is their abode." Quran [47:12]
Al-Bukhari, Muslim and others have narrated that Rasulullah sallallahu 'alayhi wa sallam said, "A Muslim eats with one intestine. A non-Muslim eats with seven intestines."
"Seven," refers to exaggeration and excess. It is said that it is an analogy of Rasulullah sallallahu 'alayhi wa sallam for a believer and his abstention; and an unbeliever and his greed. The believer thus eats to the extent of his need while an unbeliever eats lustfully and greedily, seeking pleasure. A little suffices the first; a lot is insufficient for the second.
As for the first aspect of extravagance Allah says, "Do not be extravagant."
The exception is if one intends gaining strength for worship or to entertain guests with the food.