It turns out that even moderate dehydration (which results in the loss of 3% of your body weight) can make you feel mentally sluggish and mess with your concentration. The next time you're feeling foggy or light headed, don't just assume you're in serious need of some food. Try downing a glass or two of water.
2. Cell phones
Checking your cell before bed amps up brain activity, making it harder to doze off. Plus, any electronic gadget's artificial blue light can suppress the sleep hormone melatonin. A 2011 poll by the national sleep foundation found that 20% of people ages 19 to 29 are awakened by a call, text, or e-mail at least a few nights a week. Power it down well before bedtime.
3. Undetected thyroid problems
Fatigue is one symptom of a thyroid condition called hypothyroidism, which is very treatable. Most health experts concur that every woman should have her thyroid levels tested every few years (just a simple blood test) to rule out any such conditions (they're common in women).
While working out zaps the stress hormone cortisol, prolonged sweat sessions—like, for example, regularly running for more than 30 minutes at a steady rate—can actually rev cortisol production. Interval training (bursts of intense activity) combined with strength training (free-weight and body-weight moves) helps keep cortisol in check.
5. Low iron
Iron shuttles oxygen around your body and removes waste from your cells. If you're not getting around 18 milligrams a day, your body struggles to function properly and you can feel worn out; low iron levels in your diet can cause iron deficiency anemia. If you feel sluggish, ask your doctor for a simple blood test to see if you should be taking a supplement. Hair loss or really bad periods can also be signs of low iron.
6. Too much coffee
Those who drink excessive caffeine often get a burst of energy initially, but then may crash after the effects wear off. Caffeine stimulates the central nervous system, increasing alertness and generally creating an energizing effect. In addition to occurring naturally in coffee, tea, cocoa and chocolate, caffeine serves as an ingredient in over-the-counter products such as certain headache formulas, weight-loss supplements and pills for staying awake. Too much caffeine can backfire on you and cause fatigue.
7. Environmental toxins
Many people are sensitive to environmental toxins, which could be any number of things, including the pthalates in perfume, the pcbs in plastic water bottles or the pesticides in food. All of these get in the body and short-circuit your mitochondria--the energy centers of your cells. They could also be making you tired.