8 Instant energizers -- any time of day!

Having a low-energy day? Sometimes the problem is lack of sleep, but even if you're well rested, certain diet or exercise habits or other lifestyle choices can bring on a slump. And surprisingly little things-like the size of your Starbucks order-can hurt or help your energy levels. Make some of these tweaks to recharge your batteries and power through your day.

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1. Have bran for breakfast

Eating a morning meal rich in fiber may make you more alert during the day. A Cardiff University study found that subjects who ate a high-fiber cereal in the morning showed a 10% reduction in fatigue, lower incidence of depression, and better cognitive skills. One theory: Fiber helps slow down the absorption of food in the stomach, which keeps your blood sugar levels steady to sustain energy levels for a longer period of time.

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2. Order a small latte-and sip it slowly

Experts say it's best not to rely too heavily on caffeine, but if you're an unapologetic java junkie, try spreading your intake out more evenly over the day. Mini servings of caffeine (8 ounces of coffee or less) every few hours keep you awake, alert, and focused for longer than a single jumbo one would, according to sleep experts. "When you quickly drink a large coffee, the caffeine peaks in your bloodstream much sooner than if you spread it out over time," says Harris R. Lieberman, PhD, a research psychologist with the US Army Research Institute of Environmental Medicine.

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3. Gulp some water

"Half of the people who come to me complaining of fatigue are actually dehydrated," says Woodson Merrell, MD, executive director of the Continuum Center for Health and Healing at Beth Israel Medical Center in New York City. Staying hydrated is one of the simplest ways to keep energized and focused. A recent study of athletes found that 92% felt fatigued after limiting fluids and water-rich foods for 15 hours; they also had lapses in memory and reported difficulty concentrating. Aim to drink every hour or two so you don't feel thirsty.

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4. Or steep a cup of tea

A recent report found that pairing caffeine and the amino acid L-theanine, both present in tea, decreased mental fatigue and improved alertness, reaction time, and memory. What's more, black varieties can help you recover from stress, according to researchers at University College London. In their study, adults who drank tea four times a day for 6 weeks had lower levels of the stress hormone cortisol after a tense moment, compared with those who drank a tealike placebo.

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5. Take a 10-minute walk

A short stroll can invigorate the rest of your day, suggests research presented to the American Heart Association. Women who walked briskly for 70 minutes a week (or 10 a day) reported 18% more energy than their sedentary peers after 6 months. They also felt more clearheaded and confident, had fewer aches, and hoisted groceries and climbed stairs more easily.

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6. Copy your kid's lunch
... If it's a banana and peanut butter sandwich. Bananas pack potassium, a mineral your body needs to convert sugar in your blood into energy, says energy expert Susan Lark, MD, author of The Chemistry of Success: Six Secrets of Peak Performance. The peanut butter is high in magnesium, which gives your cells much-needed energy. Aim for 320 mg of magnesium and 4,700 mg of potassium daily. Other good sources of potassium and magnesium: fruits, vegetables, beans, and nuts.

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7. Cue up your iPod

Feeling dazed at your desk? Consider listening to music while you work. One study found that employees who donned headphones while they worked were 10% more productive than without them.

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8. Order the seaweed salad

If your go-to Japanese appetizer is miso soup or edamame, consider rotating seaweed salad into the mix. It's packed with iodine, a chemical that helps maintain sufficient levels of the thyroid hormones that regulate your weight, energy level, and mood-and a new study finds you may not be getting enough of it. We tend to get our biggest dose of iodine from table salt, but among 88 randomized samples of common iodized salt brands, 47 didn't contain the FDA's recommended iodine concentration, say scientists from the University of Texas at Arlington.

Adults should get 150 mcg of iodine daily (220 mcg if you're pregnant, 290 mcg if breastfeeding). Iffy on the seaweed? Other food sources include fish and yogurt.

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