Abstarct: Overweight and obesity are a risk factor for non-alcoholic fatty liver disease (NFLD), which is increasing worldwide. The aim of the present study is to investigate the effect of dietary changes and aerobic activity on histological changes in obese male Wistar rats. For this purpose, obese male Wasitar rats were divided into four experimental groups and one control group and were subjected to a standard diet and aerobic activity for eight weeks, and the animals were given a 24-hour rest in the last training session, and their food was stopped the night before and only water was given to them and it was sent to the laboratory for the preparation of slide, staining and histological examination. Histopathological changes of liver and pancreas tissues were observed using light microscope. Results: The results showed that the obese group + standard diet + exercise had a 66% (2 grade) decrease in hepatocyte, central lobular vein, sinusoidal space and 33% decrease in hyperemia and inflammation compared to the obese group. The rest of the groups showed a degree of grade reduction in most variables compared to the obese group. The results of the present study showed that changing the type of diet and aerobic activity causes positive changes in liver and pancreas tissue of obese male rats.