Hello, It has been appreciated for a very long time that there is a complex relationship between thyroid disease, body weight and metabolism. Metabolism is determined by measuring the amount of oxygen used by the body over a specific amount of time. If the measurement is made at rest, it is known as the basal metabolic rate (BMR). In fact, measurement of the BMR was one of the earliest tests used to assess a patient’s thyroid status. Patients whose thyroid glands were not working were found to have low BMRs, and those with over-active thyroid glands had high BMRs. The way to manage weight gain is by taking the thyroid hormone medicine your doctor prescribed. A daily dose of levothyroxine (Levothroid, Levoxyl, Synthroid) will rev up your thyroid hormone production again, and with it, your metabolism. Once you’re on the right dose, your weight should stabilize, and you shouldn’t have any more trouble losing weight than anyone else. Thyroid hormone might not rid you of any weight you’ve already put on, though. To get back down to your original weight, follow a sensible strategy that combines diet and exercise. Daily workout will also give you more energy, counteracting the fatigue hypothyroidism can cause. Because an underactive thyroid can slow your heart rate. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Pervinder Rajput, General & Family Physician