Three experiments were conducted to determine the effect of body composition on the diet selected by finishing pigs. In Exp. 1 and 2 pigs were sorted into body composition groups based on ultrasound scans at the 10 th rib. In Exp. 3, barrows were randomly assigned to one of four dietary treatments. Lean gilts (Exp. 1) consumed more of the high protein diet (63.9%) than did Fat gilts (31.5%), resulting in differences in percent protein consumed. Lean barrows (Exp. 2) consumed 70.6% of the high protein diet whereas Fat barrows consumed 56.9%, but this did not result in significantly different percent protein consumed. Barrows in Exp. 3 self-selected a 16.7% CP diet, which was different from the 15.6% CP Mix diet treatment. The results suggest that allowing animals to self-select may reduce nitrogen intake, nitrogenous excretion, cost of production, and negative environmental impact.