5 Ways Your Healthy Diet is Making You Tired

Who doesn't wish for more energy at least a few dozen times a day? Of course, you know that a good night's sleep, regular exercise, and effective stress management can give you a much-needed boost. But to further figure out why you're slumping, you need to pinpoint the energy-sucks in your diet. (Hint: Those low-carb meals aren't doing you any favors.) "Our bodies rely on the energy and nutrients we get from food, so what you eat—and how and when you eat it—can either drain you or sustain you," says Jennifer Sacheck, PhD, associate professor of nutrition at the Friedman School of Nutrition Science and Policy at Tufts University. These fuss-free nutrition tweaks will give you more oomph every day.

Food Fix:

Snack early, snack often

Every time you go more than two hours or so without eating, your blood sugar drops—and that's bad news for your energy. Here's why: Food supplies the body with glucose, a type of sugar carried in the bloodstream. Our cells use glucose to make the body's prime energy transporter, adenosine triphosphate (ATP). Your brain needs it. Your muscles need it. Every cell in your body needs it. But when blood sugar drops, your cells don't have the raw materials to make ATP. And then? Everything starts to slow down. You get tired, hungry, irritable and unfocused. Grab a bite every two to four hours to keep blood sugar steady. Nosh on something within an hour of waking—that's when blood sugar is lowest.

Food Fix:

Think soluble fiber

Energy, thine enemy is a sugary breakfast: pancakes, white toast, muffins and the like. Instead, start your day with

soluble fiber (found in oatmeal, barley and nuts). "It dissolves in the intestinal tract and creates a filter that slows the absorption of sugars and fats," explains David Katz, MD, founder of the Yale Prevention Research Center and author of Disease Proof. In fact, research shows that choosing a breakfast with either soluble fiber or insoluble fiber—the kind in whole-grain breads and waffles—actually protects against blood sugar spikes and crashes later in the day. A smart start: cereals with at least 5 grams of fiber a serving and whole-grain breads with 2g per slice.

Food Fix:

Get more broccoli and kale

There's no such thing as a "wrong" vegetable, but for the most gusto, pick cruciferous ones, like broccoli,

cabbage, Brussels sprouts, cauliflower and kale. These produce rock stars contain isothiocyanates, compounds that activate a protein called Nrf2, which in turn generates mitochondria, the part of cells responsible for converting glucose into ATP. "The more mitochondria you have, the better your muscles work and the less fatigued you'll be," explains Mladen Golubic, MD, medical director of the Center for Lifestyle Medicine at the Cleveland Clinic's Wellness Institute. Toss broccoli into stir-fry; mix shredded cabbage with vinegar; or season cauliflower with turmeric, cloves cardamom, coriander and cinnamon.

Food Fix:

Beef up on iron-rich foods

Do you eat mostly vegetarian? Is your period heavy or long? Are you a coffee or tea fiend? If you answered yes to any of these, you may need more iron, key for strength and stamina. About 12% of women ages 20 to 49 may be iron-deficient. "If you're deficient, you could eat the best diet and still be exhausted," says Meridan Zerner, RD, a sports dietitian at Cooper Aerobics in Dallas. Women need about 18 mg daily until 51, and 8mg after that. Beef is the best source of heme iron, the form most easily used by the body; a 3-ounce serving has 3mg. You can get nonheme iron from plant sources, like kidney beans (5mg in 1 cup) and spinach (3mg in ½ cup cooked). To help your body absorb nonheme iron, eat vitamin C-rich foods (orange juice, berries, tomatoes) and avoid coffee and tea an hour after eating as tannic acids can block iron absorption.

Food Fix:

Hello, whole-wheat pasta and potatoes!

"Our bodies run on carbohydrates," says Zerner. "It's too bad they've gotten a bad rap." In a Tufts University study, women on a carbs-restricted diet did worse on memory-based tasks compared with women who cut calories but not carbs. And when the low-carb group introduced them back into their diet, their cognitive skills leveled out. Carbs help your body burn fat without depleting muscle stores for energy. The ideal diet is 50-55% complex carbohydrates, 20-25% protein and 25% fat. Complex carbs provide energy as they're digested, while protein and fat, along with fiber, slow the digestion process so the boost lasts a good long time. "Think about getting a mix of high-quality protein, carbohydrates and fat from whole, unprocessed foods over the course of any given day," says Dr. Katz. "That's really all we need."