Role of carbohydrate type on diet selection in neuropeptide Y-stimulated rats

We tested whether carbohydrate source (corn starch, sucrose, Polycose) influences the choice between a high-fat and high-carbohydrate diet in spontaneously feeding rats and in rats stimulated to eat by neuropeptide Y (NPY) administration or food deprivation. Rats were tested under three diet options: I) a high-fat diet versus a high-corn starch diet; 2) a high-fat diet versus a high-sucrose diet; and 3) a high-fat diet versus a high-Polycose diet. During daily and stimulated feeding rats ate more of the high-carbohydrate diet than the fat diet when the source of carbohydrate was sucrose or Polycose; however, when corn starch was provided as the carbohydrate source rats ate more of the high-fat diet. Food-deprived rats increased intake of both the high-fat and the high-carbohydrate diets, with the proportion of energy ingested from each of the diets resembling that noted during 3 days of spontaneous feeding. NPY-injected rats ate more of both the high-fat and high-carbohydrate diets during diet options I and 3, but not during option 2 when the high-sucrose and high-fat diets were offered concurrently. In that case, rats did not significantly increase their intake of the high-fat diet. Although carbohydrate source and NPY administration each influenced diet selection, altering the source of carbohydrate had a more marked effect.