Albio rats right after weaning, weighing $50{sim}55g$, were divided into the control, high-carbohydrate-, high-lipid-, and high-protein-fed groups. and were fed for 12 weeks with the respective diets to observe the increase in body weights as well as changes in the chemical constituentes and enzyme activities in the liver tissue, with the following results. (1) There was little difference in the rate of increase in the body weights among the groups, showing normal growth, except the high-protein-fed group which showed decrease in rate of body weight increase from the 7th week after feeding. (2) The liver weight was either increased after 12 weeks of feeding with the high-carbohydrate and high-Lipid diets, or showed no difference with the high-protein diet, as compared to the control weight. (3) The liver cytosol protein content was increased when fed with the high-protein diet, but decreased when fed with the high-carbohydrate and high lipid diets, as compared to the control content. (4) The triglyceride and cholesterol contents in the liver were decreased in the high-protein-fed group, but increased markedly in the high-carbohydrate- and high-lipid-fed groups as compared to the control values. (5) The hepatic glucokinase, G6PD, LDH, and fatty acid synthetase activities were increased in the high-carbohydrate and high-lipid-fed groups, and GOT and CPT activities were increased in the high-protein-fed group. From the above results. it was known that the high-carbohydrate and high-lipid diets stimulated the hepatic lipid metabolism, giving rise to lipogenesis, but the high- protein diet could prevent the lipogeuesis leading to the body weight increase.