The increase in numbers and prosperity probably refers to the priesthood, who, as they grew in numbers, became more alienated from the true God. These eat up, or fatten on, the very sins they ought to rebuke. The reference here may be either to the portion of sacrificial offerings which fell to the share of the priests, or (less probably) to the sin-money and trespass-money exacted in place of sin-offerings of 2 Kings 12:16. (On the general condition of the priesthood at this time, see W. R. Smith, Prophets of Israel pp. 99-101.)
Related Commentaries of Hosea 4:7
Hosea 4:7-8
7 As they were increased, so they sinned against me: therefore will I change their glory into shame.
8 They eat up the sin of my people, and they setd their heart on their iniquity.