Factors influencing energy intake of rats fed either a high-fat or a fat mimetic diet.

The aim of this study was to compare the effects of chronic feeding of a high-fat diet and a diet containing a fat mimetic on energy intake, body composition and tissue metabolism of mature female Sprague Dawley rats. Rats were fed a control, 25% kJ fat, diet for 10 days. Preference for this diet compared with a high-fat, 45% kJ fat, or fat mimetic, 25% kJ fat, diet was determined by offering rats two diets, in random order, for a period of 13.5 hours on three different occasions at two day intervals. Animals were then divided into three groups, receiving one of the three diets for 42 days. Dietary preference was tested again. Hepatic and muscle glucose and fatty acid utilization were measured in vitro and body composition was determined. Most of the rats preferred the mimetic diet over either control or high-fat diet, but there was no correlation between preference for a diet and intake of that diet during the experimental period. Animals fed either the high-fat or mimetic diet had greater energy intakes and body fat contents than control rats. Stepwise multiple regression determined which combination of variables correlated with energy intake of animals in each group. In rats fed high-fat diet, energy intake = 7.2 hepatic fatty acid oxidation (FAO) -0.2 hepatic glycogen - 131 muscle glycogen -0.9 hepatic fatty acid esterification (FAE) + 1.3 hepatic fatty acid synthesis (FAS) (R2 = 0.67). In rats fed mimetic diet, energy intake = 77.3 initial weight + 4.5 hepatic FAS -2.4 serum free fatty acids + 68.4 serum insulin (R2 = 0.67). These data suggest that obesity can be induced by changing the orosensory properties of a diet without changing macronutrient composition.