Illustration: Todd Detwiler
Thyroid hormone regulates how fast you burn calories. One in ten women doesn't produce enough of it—a condition known as hypothyroidism, which can lead to weight gain, depression, and fatigue. On the other end of the spectrum is hyperthyroidism, in which the thyroid gland releases too much of its hormone, causing symptoms such as anxiety, a racing heart, excessive sweating, even diarrhea.
What You Can Do
If you have hypothyroidism, a daily thyroid hormone replacement pill can help correct the imbalance. You might also want to consider eating more onion. This veggie contains kaempferol, a compound that may kick-start production of the hormone. If you have an overactive thyroid, your doctor may prescribe one of several treatments, from radioactive iodine—to slow hormone production—to surgical removal of the gland; most patients respond well once they get the proper care.