Here's Why Carbs Are Actually So Important for Your Workouts

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You've had a good night's sleep. You're well hydrated. You've built a killer Spotify playlist. Still, you have no energy. What gives?

While it's all-too-easy to fear 'em (especially in the age of paleo and keto), healthy carbs-or specifically a lack of 'em-could be the reason you're totally gassed. "Carbs should make up the majority of your diet, especially if you're active," says Kelly Pritchett, Ph.D., R.D., an assistant professor of sports nutrition at Central Washington University. In fact, healthy carbs are important-scratch that-crucial for a healthy, active lifestyle.

Of course, it's easy to have *a lot* of questions when it comes to the macronutrient (like what exactly counts as a healthy carb? or how should I be fueling my workout with carbs?). So what do you really need to know? Consider this your ultimate guide to carbs-the healthy, the not so healthy, and how they can help you feel healthier, stat.

What are carbohydrates anyway?

In addition to protein and fat, carbohydrates are one of the three macronutrients in food, and you need them for energy and fuel. When you exercise, you need something to start your engine and keep it going, and that something often comes in the form of healthy carbs. "They're our primary energy source during exercise, and we can't get to the same level of intensity if we're carb depleted," Pritchett says. Read: These carbs matter big time when it comes to working out.

Not all carbs are created equal, however. Naturally occurring sugars like fructose in fruit and lactose in dairy, sugars that are added to foods, and refined grains such as white rice are broken down quickly by your body. That means they provide almost-instant energy, but it doesn't quite last. And unless they're bundled with other nutrients, like the fiber in an apple or the protein in yogurt? They're basically "empty" calories. Other carbs, such as those found in whole grains, vegetables, and legumes take longer to digest, so you get a steadier supply of energy.

And while some carbs (think: cupcakes) are sky-high in calories, that's not always the case. "Many foods that contain carbs, such as fruits and vegetables, are low in calories and high in vitamins and minerals," says Pritchett. Other healthy carbs fall somewhere in between. Whole grains, for example, contain a lot of nutrients and calories, while low-fat dairy has a medium amount of both.

In essence, you want to always cut down on added sugar and refined grains and consider all other healthy carbs fair game.

What happens when I eat carbs?

When you eat carbohydrates, they get broken down into sugars (glucose, fructose, and galactose) and are either quickly used for energy or are stored as glycogen in your liver and muscles for use later. When you eat any type of carb, your body also releases insulin to help you regulate an increase in blood sugar.

How fast they get broken down depends on the type of carb you eat. Simple carbs quickly get broken down into your bloodstream and give you a supercharge of energy, but leave you at a low later on. Classic examples: fruit juice, white bread, white rice, cereals with little fiber, bagels, and candy. Eating these can become a vicious cycle, too, explains Wendy Bazilian, R.D., coauthor of The SuperFoodsRx Diet, because your body gets a rush and then crashes, leaving you craving a fix.

Complex carbs-your fruits, vegetables, and whole grains (with less sugar and more fiber)-are broken down at a slower rate, on the other hand, and can help keep your cholesterol levels and weight under control.

Should I eat healthy carbs before and after working out?

You've likely heard the term "carbo-loading"-and there's something to it: Most of the time, you want to fuel your body with whole-grain, high-fiber (3g or more) complex, healthy carbs. Bazilian suggests eating half a piece of whole-grain toast or half a banana 45 to 60 minutes before your workout. "The idea is to provide your body with easily digestible energy far enough in advance that your workout isn't interrupted by the digestion process," she says. Important note: There's no need to nosh if you're exercising for less than 60 minutes within a couple hours after a meal and don't feel hungry.

Working out for longer-90 minutes or more? You want to get your energy levels up so you have some ready fuel for your body to burn. That's when a serving of simple carbs (an English muffin with jelly, a bowl of cereal) comes in handy. During exercise, you want your body to focus on working your muscles, not breaking down foods with lots of fiber. So contrary to what you want to do the rest of the time, at this point you should feed your body simple sugars that are quickly absorbed and will give you bursts of energy.

If you have an endurance event such as a marathon or triathlon coming up, don't pig out on pasta the night before, though, or you might feel weighed down for the main event, says Kim Larson, R.D., founder of Total Health Nutrition. A better strategy? "You want to increase your carbohydrate intake by up to 100 grams a day-about an extra three servings-starting three days before the big event."

As for post-workout, the repair and re-growth of tissue rely not just on protein but also on replacing lost glycogen (broken-down carbohydrates) and fluids. Restore your body's energy with complex carbs-meaning fruit, grains, or vegetables paired with protein for muscle repair and growth. Good choices: yogurt and fruit, an apple and peanut butter, or a glass of skim chocolate milk. (More on that here: Exactly Why Chocolate Milk Has Been Called "The Best Post-Workout Drink")

So how many carbs do I need?

That's going to depend on a lot of different factors such as age, how much you work out, what your lifestyle is like, and what your dietary restrictions are. But Pritchett recommends getting 45 to 65 percent of your calories from carbs, depending on how much cardio you do (aerobic activity requires more carbs than Pilates, for example). "You need 130 grams a day just for your brain to function, and active women should aim for between 200 and 300 grams," she explains.

And you never want to cut carbs-or any whole food group or macronutrient-out entirely. You'll likely miss out on important nutrients, explains Tanya Zuckerbrot, R.D., author of The F-Factor Diet. "Many of the vitamins and minerals we need come from fruits and vegetables, so cutting these out can lead to deficiencies."

Even more: High-fiber carbs can help increase amounts of the feel-good hormone serotonin, which can improve mood, she says. Add healthy fats and protein and they'll keep your blood sugar steady, to boot.

And while no carb is "off limits" (hey, we all need cookies from time to time, right?), some are a healthier pick than others. To help steer your decisions, know that registered dietitians traditionally often suggest aiming for six servings of starches and whole grains, three to five servings of vegetables, three to four servings of fruits, two to three servings of dairy, no more than two servings of refined grains, and no more than one serving of "treats" a day.

Want something more specific? Use this sample menu as a guide. It adds up to nearly 215 grams of carbs, about the ideal amount for an active woman who's taking in 1,800 calories a day. (Related: How Many Carbs Should You Eat in a Day?)

• Breakfast (43g carbs): Whole-wheat English muffin with 1 slice Swiss cheese and 1 egg scrambled with 1 cup spinach + 1/2 grapefruit

• Lunch (72g carbs): Turkey sandwich on whole-wheat bread with lettuce, tomato, avocado, and cucumber + 6 ounces low-fat yogurt with 1/2 small peach, diced

• Snack (15g carbs): Apple + low-fat string cheese

• Dinner (51g carbs): 2 fish tacos made with corn tortillas, shredded cabbage and mango salsa + small side black beans

• Dessert (32g carbs): 1/2 cup light ice cream with 1/2 cup sliced strawberries