Is it Haram to waste food, or not to eat all the food on your plate?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

…It is unlawful to throw away food that is still good. Rather it should be given to the poor and the needy if possible or refrigerated for future use. It should not be disposed of unless there is fear of it causing harm to those who consume it, or that it may become disgusting for people, in this case it should be given to domestic animals, like hens, cats, etc.

However if the food is rotten, there is no objection to throwing it way. The Muslim should avoid exaggeration in expenditure. He should be moderate and should not spoil his money. Allah says: “Eat and drink but waste not by extravagance, certainly He (Allâh) likes not Al-Musrifûn (those who waste by extravagance). (Al-A’raf 7:31)

Allah also says: “And those, who, when they spend, are neither extravagant nor niggardly, but hold a medium (way) between those (extremes).” (Al-Furqan 25:67)

On the other hand, it is not obligatory to eat everything that is on the plate. Rather, one should eat little to keep healthy. The Prophet (Sallallahu Alaihi wa Sallam) said:” The child of Adam has not filled any receptacle worse than his stomach. It is sufficient for the child of Adam to eat small bits of food that keep him healthy. Now if he wants to eat much any way, he should give a third to the food, a third to the drink and a third (of his stomach) to let him breathe comfortably.”(Ahmad)

If the person eats the food and little of it remains then he should eat that.

Anas said: “The prophet ordered us not to leave anything in the plate and he said: “You do not know in which portion of your food Allah has put the Barakah “(Blessing). (Muslim)

Allah knows best.