Albert Barnes Commentary Leviticus 3:16

"And the priest shall burn them upon the altar: it is the food of the offering made by fire, for a sweet savor; all the fat is Jehovah`s." — Leviticus 3:16 (ASV)

Rather, as food from an offering made by fire for a sweet savour, all the fat shall be for Yahweh. Our bodily senses of taste and smell provide symbols of the satisfaction with which the Lord accepts the appointed symbols of true worship of the heart.

Everything that was sent up in the fire of the altar—including parts of the sin offering (Leviticus 4:31) and the burnt offering (Leviticus 1:9 and others)—was accepted as a sweet savour. However, the word "food" may have a particular suitability here in its application to the peace offering, as this offering also served as food for the priests and the offerer, thereby symbolizing communion between the Lord, His ministers, and His worshippers.

The fat is the Lord’s — The significance of this appears to be that its proper development in the animal is generally a mark of perfection.