Protein and amino acid intake in cafeteria fed obese rats.

Food selection pattern and portal blood amino acid profile were examined in rats given a cafeteria diet. Compared to standard-diet fed rats, cafeteria-diet fed rats consumed more energy. Increase in energy intake was attributable to an increase in fat intake. Protein intake was slightly higher and carbohydrate intake remained constant and was similar to levels consumed by standard-diet fed rats. The cafeteria rats took up higher quantities of Phenylalanine+Tyrosine, Arginine, Histidine, Lysine, Leucine, Isoleucine, Valine, Threonine, and Glycine, lower quantities of Tryptophan and the same quantity of Methionine+Cysteine vs. control rats. Portal concentrations of Serine, Threonine, Tryptophan and Lysine were significantly higher in cafeteria-diet fed rats than in standard-diet fed rats. This can be interpreted in such a way that, on the whole, the quality of protein ingested by cafeteria and control rats is similar. No statistical differences in the ingestion of individual amino acids were observed between different days of the period of cafeteria diet feeding, thus the idea of a strict control of protein ingestion irrespective of the obese status is reinforced.