EFFECT OF A HIGH-FAT DIET ON ENERGY-BALANCE AND THERMAL EFFECT OF FOOD IN HYPOTHYROID RATS

We have carried out measurements of energy balance in hypothyroid rats fed a low-fat or a high-fat diet for eighteen days. We have also meas ured cephalic and processing thermic effect of food (TEF) after a low- fat or a high-fat meal. Body lipid gain, carcass lipid content and gro ss efficiency were significantly (P <0.05) higher in hypothyroid rats fed a high-fat diet compared with hypothyroid rats fed a low-fat diet, while metabolizable energy intake and energy expenditure remained unc hanged. Cephalic TEF after a low-fat meal was significantly (P <0.05) lower in hypothyroid rats fed a high-fat diet compared with hypothyroi d rats fed a low-fat diet, while it was significantly (P <0.05) higher after a high-fat meal than after a low-fat meal in hypothyroid rats f ed a high-fat diet. No significant variation was found in processing T EF after a low-fat or a high-fat meal. Our results indicate that hypot hyroid rats are unable to develop increased energy expenditure and inc reased TEF in response to a high-fat diet.