Weight gain after thyroid surgery may be caused by low activity after surgery which requires increased exercise to control weight, or it may be caused by thyroid hormone deficiency which requires standardized treatment under the guidance of a doctor. 1. Low activity level after surgery: Some patients do not pay attention to daily exercise after surgery, resulting in a slight increase in weight. You can exercise reasonably under the guidance of your doctor to control your weight and maintain your physical and mental health. 2. Thyroid hormone deficiency: If the body does not produce enough thyroid hormone after thyroid surgery, it will lead to lower basal metabolism and weight gain. It is recommended to go to the hospital in time to supplement exogenous thyroid hormone, such as levothyroxine, and follow the doctor’s instructions for regular review of thyroid hormone levels. Weight gain after thyroid surgery can also be caused by other reasons, it is recommended to go to a specialized hospital for timely review and treatment as prescribed by the doctor.