Postprandial blood triglyceride is believed to be a risk factor for coronary artery disease. In this study, rats were fed a fat emulsion orally to study the effect of daily diet on postprandial blood triglyceride. First, rats were fed different volumes of dairy cream or corn oil emulsions. The resulting serum triglyceride levels were influenced by time and dose. Second, the maintenance diet for rats was switched to a high-fat or a low-fat diet, and an oral fat tolerance test was conducted. A few days of high-fat feeding hastened the peak of serum triglyceride after administration. Two weeks of high-fat feeding elevated basal serum triglyceride, and the peak of postprandial triglyceride was submerged. The short-and medium-term fat content of the daily diet clearly affects the results of a fat loading test.