Thyroid and Weight FAQs

source: American Thyroid Association

What is the Relationship Between Thyroid and Weight?
It has been appreciated for a very long time that there is a complex relationship between thyroid disease, body weight and metabolism. Thyroid hormone regulates metabolism in both animals and humans. 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). Indeed, 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 overactive thyroid glands had high BMRs. Later studies linked these observations with measurements of thyroid hormone levels and showed that low thyroid hormone levels were associated with low BMRs. Most physicians no longer use BMR due to the complexity in doing the test and because the BMR is subject to many other influences other than the thyroid state.