Abstarct: Background and Aim: Childhood obesity is on the rise worldwide and has numerous effects on other body tissues including the thyroid. The present study investigates the effects of obesity on thyroid tissue and also the complementary effect of garlic and stevia extract along with aerobic activity on thyroid tissue and thyroid hormones. Materials and Methods: 35 Wistar rats were randomly divided into 7 control groups: healthy, obese, garlic, stevia, aerobic, garlic + aerobic and stevia + aerobic. Aerobic exercise including 30 minutes per day, 8 / m / min 5 days a week and garlic and stevia extract at a concentration of 250 mg / kg were added to the daily water intake. Thyroid tissue was sent to the relevant laboratories for histopathological studies and 5 cc of blood for TSH, T3 and T4 studies. One-way ANOVA, Kruskal-Wallis and LSD post hoc test were used to determine the differences between groups and a significance level of 0.05 was considered. Results: The results showed that 12 weeks of high-fat diet in rats caused a significant increase in serum levels of TSH and T3 compared to the healthy control group (p >0.05). In addition, serum T4 levels of obese rats increased significantly compared to healthy control group (p <0.05). On the other hand, histological results showed that obesity causes moderate to severe structural changes in thyroid tissue. Conclusion: The above results showed that induction of high fat diet causes significant structural changes in the follicular, para-follicular and colloidal sections of male Wistar rats and the combination of aerobic activity with garlic and stevia can be more beneficial in reducing these complications.