Abstract: Objective     To observe the effect of high-calorie diet on the establishment of obesity model in rats, and the differences in modeling between two different stocks of rats, and to compare the differences of obesity evaluation methods and obesity-sensitive animals screening methods, providing a reference for the preparation of animal models to study the function of weight loss products. Methods    Total of 120 SD (Sprague Dawley) and 120 Wistar male rats were randomly divided into 2 groups (blank control group and model group) by body weight, with 60 rats in each group. The rats in blank control group were given basic diet, and the rats in model group were given improved high-calorie diet. The body weight and body length of the rats were recorded once a week, and the feeds were weighed twice a week to calculate the Lee's index, food intake and food utilization for 6 weeks. After 2 weeks and 6 weeks of feeding, 30 rats in each group were respectively selected to measure the biochemical indicators, and the fat around the kidney and the testis was dissected and weighed to calculate the fat/body weight ratio. The correlations of weight gain and Lee’s index with obesity and obesity sensitivity were analyzed. The correlation between obesity and weight gain after eliminating the last 1/3, 10%, and 20% rats with weight gain after 2 weeks of feeding were compared. Results   Compared with blank control group, the body weight, Lee's index, weight gain, food utilization rate, body fat weight and fat/body weight ratio, as well as the serum levels of glucose and triglyceride in the two stocks of rats in model group were increased, while the food intake and the serum level of high density liptein cholesterol (HDL-C) were decreased (all P<0.05). There was no significant difference in each index of model group between SD rats and Wistar rats (P>0.05), but the differences in body length, Lee's index and food utilization rate of the two stocks of rats in blank control group were occasionally appeared during the experiment (all P<0.05). There was significant difference in serum level of HDL-C between SD rats and Wistar rats in the blank group at 2 and 6 weeks of feeding (P<0.05). The correlations of body weight gain with obesity and obesity sensitivity of the two stocks of rats were greater than those of Lee's index with obesity and obesity sensitivity (both P<0.05). When eliminating the last 10% or 20% rats with weight gain, the correlation between weight gain and obesity was better as compared with eliminating last 1/3 rats; the correlation coefficient was the highest when eliminating the last 10%. Conclusions    The obesity model of rats induced by the improved high-calorie diet can be successfully established in SD rats and Wistar rats, and there is no significant difference between the two stocks. As an index of obesity evaluation and obesity sensitive rat selection, weight gain is better than Lee's index. Eliminating the last 10% rats with weight gain is useful for selecting the obesity sensitive animals. 

Key words: High-calorie diet, Obesity model, SD rats, Wistar rats