The thyroid is a butterfly-shaped gland located in the front of the neck, below the larynx. The gland consists of follicular cells that produce the hormones — thyroxine and triiodothyronine — which play an important role in metabolism.

Doctors prescribe thyroid medication, usually levothyroxine (Synthroid, Levoxyl, Unithroid), to boost your thyroid hormone levels when they are too low. There are no recommended dietary restrictions for people taking thyroid medication.

An underactive thyroid means your thyroid gland produces less than the normal amount of thyroid hormone. Having an underactive thyroid is also known as hypothyroidism and can create a host of different health concerns and symptoms.

The thyroid gland helps regulate the body's metabolism and as such can affect your weight. Although supplemental thyroid hormone may help with unwanted weight gain caused by thyroid dysfunction, synthetic thyroid hormone is a prescription medication that should only be taken by people with a documented thyroid problem.