The young rats （3 weeks） were randomly divided into control group， model group， low dose of limonin group （12.5 mg·kg^－1）， medium dose of limonin group （25 mg·kg^－1） and high dose of limonin group （50 mg·kg^－1）， with 10 rats in each group. Except for control group， the rats in other groups were fed with high-fat diet to establish the nutritional obesity rat models. After successful modeling， limonin was administered in the rats in low，medium and high doses of limonin groups，once a day for 4 weeks. The body weights of rats in various groups were recorded before and after administration， and the Lee’s index and fat coefficient were calculated. The levels of total cholesterol （TC）， triglyceride （TG）， low density lipoprotein cholesterol （LDL-C） and high density lipoprotein cholesterol （HDL-C） in serum of the rats in various groups were detected. HE staining was used to observe the pathomorphology of liver tissue and the fatty deposition in liver tissue of the rats in various groups.The structural changes of intestinal microbiota in the rat feces were analyzed by 16S rRNA sequencing.

Compared with control group， the body weight， Lee’s index and adipose coefficient of the rats in model group were significantly increased （P<0.05）， the levels of TC， TG and LDL-C in serum were significantly increased （P<0.05）， and the HDL-C level was significantly decreased （P<0.05）； steatosis and adipose accumulation in liver could be seen； in the feces， the relative abundance of Firmicutes and Spirillae was significantly increased （P<0.05）， while the relative abundance of Bacteroidetes and Lactobacillus was significantly decreased （P<0.05）. Compared with model group， the body weights， Lee’s indexes and adipose coefficients in medium and high doses of limonin groups were significantly decreased（P<0.05）， the levels of TC，TG and LDL-C in serum were significantly decreased （P<0.05）， and the HDL-C levels were significantly increased（P<0.05）； steatosis and adipose accumulation in liver were significantly improved； in the feces， the relative abundance of Firmicutes and Spirillae was significantly decreased （P<0.05），while the relative abundance of Bacteroidetes and Lactobacillus was significantly increased （P<0.05）.There were no significant differences in the above indexes between low dose of limonin group and model group （P>0.05）.

Limonin can improve obesity in the nutritional obesity rats by regulating lipid metabolism and gut microbiota structure.