Rats were given diets ad libitum which varied in the amount (5 or 15%) and kind of fat [coconut oil (CNO) vs corn oil (CO)]. Animals were injected either with hexobarbital or pentobarbital and sleeping time was recorded. With animals eating a low fat diet, there were slight differences between the CNO vs CO groups. At the higher fat level, animals receiving the polyunsaturated diet slept more than twice as long as compared to animals eating a diet with saturated oil. Simultaneous injection with carbon tetrachloride significantly increased the sleeping time between the two dietary fat groups. Also, the kind of protein and level of fat in the diet had an influence on sleeping times. It was concluded that both the quality and quantity of fat as well as the quality of the protein can influence drug metabolism.