When is your daily low point--that moment when you feel your spirits and energy flagging? Don't tell us, we know. We sifted through the very latest research on sleep, metabolism, stress, and chronobiology to identify the times when you are most vulnerable to fatigue--and, with expert help, devised a foolproof plan to help you combat it. These eight just-discovered strategies ensure you will wake up refreshed and recharged, remain alert throughout the day, and wind down just in time for a good night's sleep. Power walk, anyone?

Brighten your morning

Old Science: Let your body sleep for as long as it needs.

New Science: Get up at the same time, and bathe yourself in light. It enables your circadian rhythms, which are governed by your body's "master clock" in the hypothalamus gland, to stay in synch with the 24-hour day. In the absence of light, your body's sleep-wake cycle wants to delay by an average of 12 minutes every day and work on a 24.2-hour rhythm. (Scientists don't understand why, but think it may relate to the sun's seasonal shifts.) "That means your body wants to keep pushing your bedtime to later," says Mariana Figueiro, PhD, program director of Rensselaer Polytechnic Institute's Lighting Research Center. "But if you let that happen and still have to get up at the same time every day, you're going to be tired."

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To keep your circadian rhythms in time with the 24-hour day (when they get out of whack, you feel like you're jet-lagged), head to the light as soon as you get up, even on a Saturday when you've decided to sleep in.

Try this: You need 30 minutes of exposure to light first thing. An easy way to get it is to go for a half-hour stroll outdoors while sipping your coffee. Or have your breakfast by a sunny window. If your schedule requires you to rise when it's dark outside, consider investing in a light therapy box ($174; Light Therapy Products) with 20 times the intensity of average indoor lighting, which people use to treat seasonal affective disorder (SAD). No light box? Crank up the lights--every little bit may help.

Put more protein in your diet

Old Science: To sustain energy, load up on carbs.

New science: Limit them. Although they can provide a burst of "quick burn" fuel, carbohydrates are an energy drain if you consume too many. Women who reduced the amount of carbohydrates in their diets and raised the amount of protein reported feeling more energetic, in recent research done by Donald K. Layman, PhD, a professor of nutrition at the University of Illinois. "That's been absolutely consistent in all our studies," he says.

Try this: Keep your daily intake of healthy carbs below 150 g, best apportioned like this: five servings of vegetables; two servings of fruit; and three or four servings of starchy (preferably whole grain) carbohydrates, such as bread, rice, pasta, or cereal. You might, for instance, start your day with a breakfast of one slice of bread or one-half of an English muffin, one egg, a slice each of ham and cheese, and a glass of milk. Lunch could be an open-faced sandwich of one slice of bread, 2 to 3 ounces of meat, and 1 ounce of cheese; two servings of vegetables; and an apple. Dinner should consist of 6 ounces of lean meat, three servings of vegetables, one serving of fruit, and one or two servings of starchy carbs.

Postpone Your Pick-Me-Up

Old Science: Perk yourself up with a midmorning coffee break.

New science: Have your latte later. That's when you'll really need it. Caffeine keeps you operating at a high level by blocking the effects of adenosine, a sleep-inducing brain chemical that accumulates as the day wears on. By the time adenosine builds up to the point where you start feeling sleepy--generally, late in the afternoon--the effects of your morning caffeine will have worn off, says James K. Wyatt, PhD, director of the Sleep Disorders Service and Research Center at Rush University Medical Center.

Try this: You can stay alert by drinking about 2 ounces of coffee (equal to a large shot glass) several times throughout the day, Wyatt found in a recent study. But you don't have to go to all that trouble. "Having 1/2 to 1 cup of coffee or its caffeine equivalent during the late afternoon, when the pressure to sleep is high, will keep you energized," he says. If you're highly sensitive to caffeine's effects, you should push your break back to early afternoon so you don't have difficulty falling asleep at night, he advises.

Enjoy every meal by the clock

Old Science: "Grazing"--eating several small meals a day when you feel hungry--keeps your energy levels high.

New Science: Eat your meals at the same time every day. Your body's caloric needs are closely tied to its other daily rhythms, including when you get up and go to bed and when you expend the most energy (during your late-day fitness walk, for example). "What will make you tired is if your body expects a 7 o'clock breakfast and a 12 o'clock lunch and you skip one of those," says Layman. "Chaotic eating leads to greater hunger and overeating."

Try this: Prepare your breakfast the night before so you're sure to start the day with a boost even if you're running late. Pack a lunch to take to work in case you can't get away from your desk midday. Make several meals on the weekend that you can quickly heat up so that you and your family eat dinner at the same time every night. That way, you'll all have enough energy for an after-dinner badminton game.

Meditate in short bursts

Old Science: Meditate for at least 20 minutes to reduce stress.

New science: Get the same results with a very brief session. "Even in the span of 3 minutes, meditation can decrease the stress hormones that tense your muscles and constrict your blood vessels," says Judith Orloff, MD, a psychiatrist at UCLA and author of Positive Energy . "It increases endorphins, too." Quick time-outs throughout your workday are also easier to fit into a busy schedule than a longer one at the end.

Try this: Find a quiet place where you won't be interrupted. ("In a busy office, that may even mean going into the bathroom," says Orloff.) Sit down and close your eyes. Listen to your breath as you slowly inhale and exhale, and when thoughts intrude, imagine that they're like clouds floating by in the sky. Then visualize something or someone who makes you happy. It could be someplace you've been on vacation, someone you love, or something you love doing (like lounging in a fragrant bath).

Step outside during late-day slumps

Old Science: Afternoon droop? Take a power nap.

New Science: Illuminate yourself outdoors. Just as it does in the early morning, light later in the day may blunt an afternoon energy dip, which often comes on like clockwork. "Because of the way the homeostatic and circadian systems interact, most people feel a lull 17 to 18 hours after they went to bed the previous night," says Figueiro.

Try this: Step outside into revitalizing sunlight for a short walk. Vary your routine by taking a different path every day, doing a short errand, or catching up with a friend on your cell phone. If you can't get outside, plant yourself next to a window, open the shades wide, and look out. (One day your employer may even be able to help: Philips Electronics is making a system for offices called Dynamic Lighting that alters the light level throughout the day--raising it in the afternoon, for instance, to counteract the postlunch dip that many workers experience.)

Start your workout with a song

Old Science: Get primed for your workout with a light snack.

New Science: Jazz yourself up with music instead. Exercise is a prime energy booster, but what if you're too tired for an antifatigue workout? Put in your earphones while you lace up your walking shoes: Music will help you forget you're whipped. Volunteers who worked out for 30 minutes while listening to tunes felt they weren't exerting themselves as much as when they exercised without music, Japanese researchers reported recently in the Journal of Sports Medicine and Physical Fitness .

Try this: Load your iPod or mix CD with your favorite up-tempo tunes. If you're the literary type, an audiobook can also help distract you from feelings of fatigue.

Turn down the right lights

Old Science: Viewing TV before you go to bed will keep you awake.

New Science: Watching TV is okay, but looking at your computer is not. "Studies show that very bright light--the equivalent to outdoor early morning light--will increase brain activity," says Figueiro. "Our work has shown that you can increase alertness with far less." Some scientists believe that the light emitted by a computer monitor late at night can do just that, confusing your body's sleep-wake cycle--particularly when combined with the stimulation of an engaging video game. Wind down by watching television instead. Most people sit far enough away from a TV set (at least 15 feet) to be unaffected by its brightness. Better yet, read a book or magazine. Just make sure the light you use doesn't exceed 60 watts.

Try this: Log off at least an hour before you go to bed.