The fat fear of decades past has given way to a new anti-carb movement. With trendy eating styles like Paleo, the Whole30 diet, and the ketogenic diet as popular as ever, it seems like everyone is ditching bread (and maybe even oatmeal!) these days. But what’s a life without carbs? Besides sluggish, crabby, and riddled with brain fog, that is.

After all, when most people cut carbohydrates, they are forgetting (though maybe they never knew in the first place) the fact that carbs are a macronutrient, meaning that people need to consume them in large quantities for optimal health, explains registered dietitian and certified diabetes educator Vandana Sheth, R.D.N., C.D.E, spokesperson for the Academy of Nutrition and Dietetics.

“Carbs are one of the best sources of energy,” Sheth says. “When we drastically cut all carbs from our diet, we are making our bodies work less efficiently.” Like protein and fat (the other two macronutrients), carbs can be broken down in the body to yield ATP, a.k.a. cellular energy.

That’s especially important when it comes to exercise. When performing high-intensity workouts like strength training or max effort running or cycling, the vast majority of your energy comes from a combination of glucose (the sugar you break carbs down into) in your bloodstream and glycogen (carbs stored in your liver and muscles). If you don’t have enough carbs in the tank, your workout performance—and thus the amount of calories you burn and muscle you build—suffers, Sheth says.

What’s more, carbs are crucial to your body’s ability to recover after every workout, explains Georgie Fear, R.D., C.S.S.D., author of Lean Habits for Lifelong Weight Loss. So without them, your workouts become a greater and greater stress on your body, breaking you down rather than building you up. “Athletes with inadequate carb intake place themselves at increased risk for overtraining syndrome, immune system impairment, and thyroid and sex hormone abnormalities,” she says.

Related: 4 Possible Reasons Why You Still Feel Wrecked Days After A Workout

Plus, all macronutrients aside, it’s important to remember that carbs don’t end up on your plate in isolation. Many carb-containing foods (we will get to exactly what those are later) are rich in nutrients like folic acid, magnesium, iron, B vitamins, and fiber—all of which are necessary for adequate health, and that includes a healthy bodyweight. By drastically cutting carbs, you may be risking nutritional deficiencies that put your general health at risk, while potentially also spurring weight gain.

Whole vs. Refined: What’s It All Mean?

‘Whole, refined, complex, simple’… these carb-related terms get thrown around a lot, especially when it comes to weight loss. After all, some are far better at promoting healthy weights than are others, which is why it’s so important to understand what they really mean.

Most simply put, whole carbs are carb-containing foods that come pretty much straight from nature, with tons of fiber and vitamins and minerals. Examples include fruit, veggies, legumes, potatoes, dairy, quinoa, oatmeal, and even whole-wheat bread and pasta. Refined carbs, however, have been significantly altered through processing. During this processing, sugars are often added and fiber and other nutrients are stripped away. Common examples of refined carbs include white bread and pasta, desserts, candy, and soda. It’s pretty obvious which foods are going to support your weight-loss efforts, right?

Aside from the differences between nature-made and factory-produced carbs, it’s also important to know the differences between complex and simple carbs. Complex carbs have molecular structures that are long and branched, meaning that they take longer for your body to digest, make you feel fuller, and also feed the good bacteria in your gut. Complex carbs also contain fiber, and one study published in Annals of Internal Medicine found that increasing fiber intake may be as equally effective a weight-loss strategy as going on a full-fledged ‘diet.’ Examples of complex carbs include whole grains, legumes, potatoes, and other starchy vegetables.

Simple carbs, however, are easier for the body to break down and digest—and tend to be somewhat synonymous with refined carbs like sugar. But, there are a couple of important exceptions: fruits and dairy. While fruit and dairy contain simple carbohydrates, those carbohydrates can provide a great, quick energy boost during an afternoon slump or before a workout, and are also jam-packed with other nutrients like fiber and antioxidants (in the case of fruit) and protein, healthy fats, calcium, and vitamin D (in the case of dairy).

Your move: Focus on swapping out refined carbs for whole ones whenever possible, and while it’s good to make sure that the bulk come from complex sources, it’s still important to include some healthy simple carbs like apples and Greek yogurt.

Still, that doesn’t mean that you have to cut out refined carbs entirely. Added sugars and white bread won’t derail your health in a single portion. There’s room for the occasional low-nutrition treat in an overall healthy diet, plus they can be a big relief mentally, says Fear.

“I teach my clients to build daily meals with whole food carbohydrates, such as beans, oatmeal, sweet potatoes, and fruit, in proportion to their activity needs, and to choose only their absolute favorites when it comes to working in low-nutrition starches and sugars,” Fear says.

How Many Carbs Should You Eat to Lose Weight?

No matter what carbs you are eating, it’s important to remember that getting too many calories from any macro (carbs, included) can lead to weight gain. So, yeah, you need to keep your portions in check.

“I encourage my clients to practice skills that help them avoid excess portions of carbs, like having something sweet only after a healthy meal, eating mindfully, and, if needed, developing strategies for squashing the temporary urge to go for seconds,” says Fear. Try grabbing a glass of water (thirst loves to masquerade as hunger!) and ask yourself, “Am I really hungry, or do I just want to eat?”

Related: How Much Protein Do You Really Need?

Currently, the National Academy of Medicine recommends that the average person eat at least 130 grams of carbs per day (you’ll get that amount from 10 slices of whole-wheat bread) for proper brain function, but the exact amount you need varies depending on your weight and activity levels.

So, as a general rule of thumb, anyone who is working out regularly and wants to lose weight should shoot for consuming about three grams of carbohydrates per kilogram of bodyweight (one kilogram equals 2.2 pounds) each day, Fear says. So, for instance, a 200-pound (91 kg) man would need to get roughly 273 grams each day.

Ideally, those carbs would be spaced out relatively evenly over the course of the day through both meals and snacks so that your body stays continually fueled. What’s more, when you stockpile your carbs into any one meal, you risk consuming more energy than you need at that moment to keep your glycogen levels topped off. When this happens, any extra energy tends to be stored as fat, Fear says.

Another way to think about it if you’d rather eyeball your portion sizes than track your macros, is eating one to two servings of carb-rich foods at every meal, Sheth says. What’s a serving? Some examples include ½ cup of lentils, a slice of whole-wheat bread, ½ cup vegetables, a piece of fruit, or ½ cup whole-wheat pasta or grains.

Pin this handy infographic for an easy-to-reference guide to dropping pounds without sacrificing carby goodness: