More studies are needed on the hypertriacylglycerolemic effects of low fat and high carbohydrate (LF-HC) diet in young population, especially Chinese who generally have a diet containing lower fat and higher carbohydrate. To test them in a young Chinese Han population, 56 healthy subjects (22.89 +/- 1.80) years were given regular diet of 31% fat and 54% carbohydrate for 7 days, followed by LF-HC diet of 15% fat and 70% carbohydrate for 6 days, without total energy restriction. After the LF-HC diet, the male experienced an increase of high density lipoprotein (HDL) cholesterol and decreases of weight, body mass index (BMI), total cholesterol (TC), and LDL (low density lipoprotein) cholesterol (P < 0.05). The female experienced increased serum triacylglycerol and insulin, and decreased TC and LDL cholesterol (P < 0.05). When BMI was taken into account, all the subjects with low, medium, or high BMI experienced decreases of TC and LDL cholesterol although some changes were not significant. No significant decrease of HDL cholesterol was found, while significantly increased HDL cholesterol and apolipoprotein A-I (apo A-I) were found in the male subjects with low or high BMI (P < 0.05). Significant increase of triacylglycerol was observed only in the female subjects with low or medium BMI. In conclusion, subjects with different BMI and gender have different triacylglycerol and HDL cholesterol responses to LF-HC diets, and significant increase of HDL cholesterol and apolipoprotein A- I were observed in some young male subjects.