Small but powerful, your thyroid controls your metabolism and affects many other processes in your body, including maintaining your energy levels in addition to your heart rate, cholesterol levels, body weight, digestion and muscle function. 

Keep yours in check by maintaining a healthy body weight (studies show that women with a BMI over 40 have a slightly lowered thyroid function), getting adequate iodine in your diet (from sources such as seafood), and speaking with your doctor if you experience symptoms of a thyroid disorder, such as unexplained fatigue, weight gain/loss, changes in mood and/or hair loss. The American Thyroid Association recommends that women over 35 have a blood test to detect thyroid problems every five years.

Magnesium is needed for more than 300 biochemical reactions in your body, including breaking down glucose into energy. When your levels drop, so does your power. You need about 320 milligrams of magnesium daily to stave off fatigue (a common symptom of magnesium deficiency) and keep your body functioning optimally. 

Some of your best bets for dietary magnesium include dry-roasted almonds (80 milligrams for one ounce), spinach (78 milligrams a half cup, frozen) and wheat bran (69 milligrams for a quarter cup).

For an instant energy booster, try this technique: sit comfortably with your neck and spine straight and close your eyes. Place one hand on your chest and one on your belly. 

Breathe slowly and deeply, feeling your abdomen soften and relax. Continue breathing in this way, saying the word “soft” in your mind as you inhale and “belly” as you exhale. Continue until you feel relaxed and refreshed. 

http://www.oxygenmag.com/Health/Articles/3-ways-to-fight-fatigue.aspx