Enhanced acceptance and metabolism of fats by rats fed a high-fat diet.

Rats fed a high-fat diet show greater acceptance of and preference for pure fats than do rats fed a high-carbohydrate diet. We tested the hypothesis that this differential intake of fat was due to diet-induced modifications of lipid absorption and oxidation. After an intragastric load of corn oil, rats adapted to a high-fat diet had greater increases in plasma triglyceride and ketone levels and a lower percentage of fecal fat than did rats adapted to an isocaloric high-carbohydrate diet. High-fat-fed rats given corn oil containing [14C]palmitic acid expired 14CO2 more rapidly and to a greater extent than did rats maintained on a high-carbohydrate diet. These results show that the greater acceptance of fat by rats fed a high-fat diet is associated with an increased capacity to absorb and oxidize fat.