What is the link between a person's thyroid and their weight?

Thyroid is one of the six hormones that affect weight gain. What it does, it regulates how fast you burn food. If you are hypothyroid, where your thyroid level is low, then you're not going to burn the calories. You're going to hold onto those calories. If you're hyperthyroid, where your thyroid gland is overactive, then you're going to run through those calories, and you actually will lose weight. It's a very important link.