ABSTRACT
Background and Objectives: Obesity is a global health problem that could lead to cardiovascular disease, diabetes and cancer. Polygenic obesity is caused by multiple factors, such as lack of exercise and excess food intake. In this study, we evaluated effects of 12 weeks of high-intensity interval training (HIIT) and isocratic moderate-intensity training (MIT) on anthropometric indices and insulin resistance in rats fed with a high-fat diet (HFD). 
Methods: Twenty-five male Wistar rats (mean age of 5-6 weeks) were divided into three groups: control group (HFD, N=5), HFD+ MIT (N=10) and HFD+ HIIT (N = 10). After placing the subjects on a HFD for 13 weeks, the exercise groups performed trainings for 12 weeks. 
Results: Body mass index and Lee index decreased significantly in both training groups (P≤0.05). There was no significant difference in insulin resistance between the three groups (P>0.05).
Conclusion: Based on the results, it can be concluded that HIIT is more effective than MIT in reducing some of the obesity markers in obese rats fed with a HFD. However, this type of training has no significant impact on insulin resistance.
Keywords: Obesity, High Intensity Interval Training, High-Fat Diet, Body composition Indexes.