**Is obesity a cause of thyroid cancer?!** Being overweight is often one of the causes of various diseases or even the aggravation of their symptoms. For this reason, by researching the effects of excess weight on the development of various diseases, researchers try to encourage people to manage their weight and follow a healthy diet. Recently, in the American Thyroid Association (ATA), an article was published under the title of examining obesity and thyroid cancer, which we will discuss below. It should be noted that thyroid cancer surgery is one of the main ways of its treatment. But considering the existence of this connection, we recommend that you take your weight management more seriously. ### **increase in the incidence of thyroid cancer** Endocrine malignancy is known as the most common thyroid cancer worldwide. This disease affects mostly women and is the second most common disease in young women. In recent years, the prevalence of DTC (malignant thyroid growth) and especially PTC (papillary malignant growth) has increased dramatically worldwide. Although the exact reason for the increase in thyroid cancer is still unknown. But an analysis of Cancer Surveillance, Epidemiology, and End Results (SEER) registry data from 1980 to 2005 showed an increase in the prevalence of larger tumors. Environmental factors and lifestyle are among the causes of this disease. The most important risk factor for malignant thyroid growth is exposure to radiation, which increases the risk of malignant thyroid disease from 5% to 50%. Among other factors that have been studied are: - Smoking - Diabetes - obesity - Insulin resistance syndrome that is associated with weight gain. ### **How is obesity defined in this article?** In recent decades, the prevalence of obesity and overweight has increased dramatically worldwide. According to the World Health Organization (WHO), body mass index or BMI, which is calculated as weight in relation to height (kg/m2), is used as a measure for body fat. For health, BMI between 18.5 and 24.9 kg/m2 is recommended. People with BMI (25-29.9 kg/m2) are in the overweight range and are at higher risk of obesity, but obesity occurs in people with BMI greater than 30 kg/m2. ### **The relationship between obesity and thyroid cancer** In recent years, many studies have investigated the relationship between obesity and thyroid cancer. It is estimated that an increase in BMI (height to weight ratio) increases the risk of thyroid cancer by 30%. There are many studies that show that obese people are more prone to thyroid cancer and obesity causes the spread and development of thyroid cancer. Obesity is a chronic inflammatory condition associated with activation of the immune system, increased inflammatory factors, and the production of various cytokines and adipokines. These elements may directly or indirectly change cell proliferation and cause tumorigenesis in various tissues, including the thyroid gland. Therefore, a healthy diet with adequate amounts of fruits and vegetables and daily physical activity may be effective in reducing the risk of thyroid cancer. As we said, two new articles on the relationship between obesity and thyroid cancer have been presented in the American Thyroid Association