SummaryThe effects of dietary 1,3-diacylglycerol-rich oil (DG oil) on biochemical find ings related to glucose and lipid metabolisms were investigated in comparison with triacyl glycerol oil (TG oil) in normal rats. Young (7wk-old) and old (8mo-old) rats were fed a syn thetic diet containing 10% (by weight) DG or TG oil for 1, 4, 8, or 12wk. The body weights, epididymal and perirenal adipose tissue weights, and feed efficiency were not significantly different in the dietary oil groups during any feeding period. The plasma and liver triacyl glycerol concentrations were not different in the dietary groups, except that the plasma tria cylglycerol concentrations were rather lower only in the portal vein of rats fed DG oil. The plasma glucose and free fatty acid concentrations were significantly higher in rats fed DG oil as compared to TG oil. In the old rats fed DG oil for 8wk, the fasted plasma glucose and in sulin concentrations were elevated and glucose intolerance was observed. The insulin re ceptor expression was not different due to dietary oil, but was markedly reduced with aging. Thus, the anti-obesity and lipid-lowering effects of dietary DG oil were not found. Moreover, it appeared that the glucose intolerance might be induced by dietary DG oil, particularly in the old rats.