Protein deposition rate was measured in 100 lean and obese pigs of both sexes (boars and gilts) fed ad lib. The intakes of digestible ideal protein (DIP) and deposition rates of body protein was used to calculate conversion ratios of DIP to body protein at various livemasses for the different groups. The efficiency of DIP conversion to body protein decreases with increased bodymass. Estimations of DIP requirements were finally made.