Low-carb diets are trending—do we even need the macronutrient at all?

Americans certainly have a love-hate relationship when it comes to carbs. European and Asian cultures steadfastly make room for pasta, bread, and rice on their plates, but here in the States, carbs are like fanny-packs: in one day, out the next (and then, back in again?). With the low-carb, high-fat ketogenic diet dominating as the eating plan of the moment, the current consensus seems to be that carbs are no good.

Keto devotees limit their carb intake to just 5 to 10 percent of their diet—vastly lower than the Dietary Guidelines for Americans recommendation that 45 to 65 percent of overall calories come from the macronutrient. The discrepancy between the recs is so big, it feels like both can’t be healthy. So, what’s the deal? Are carbs a vital part of your diet or not?

First, it’s important to know the difference between the various types of carbohydrates out there. “Simple carbs are found in foods like sugary soda and bread, which get absorbed in the body quickly,” explains Wahida Karmally, PH, RDN,CDE, a doctor of public health and special research scientist at Columbia University. “But foods such as vegetables, fruits, nuts, and whole grains have complex carbs, which are full of more nutritional benefits and get absorbed slower.” So when experts talk about carbs being “bad,” it’s mainly the first category they’re discouraging—there is merit to consuming the second category of carbohydrates (more on that in a sec).

Functional medicine practitioner Anthony Gustin, DC, is such a big believer in a low-carb diet that he founded a whole keto company, Perfect Keto. As you might guess, he’s of the mind that you can totally live without carbs—of all types. “Carbohydrates are not important at all,” he says bluntly, saying that while the body can put them to good use, it’s possible to survive without consuming anything at all. “They can be used for energy, but they don’t have to be used for energy.”

Gustin explains that when you do eat carbs, the body breaks then down and converts the components to glucose, which then goes into the bloodstream. “Then it’s used for maintenance of red blood cells, brain function, and bodily functions.” Sounds pretty important, right? But while Gustin says blood glucose is indeed vital for fueling the body, breaking down carbohydrates isn’t the only way to make it.

He explains that during a process called gluconeogenesis, non-carbohydrate compounds, like amino acids from protein, are converted to glucose for energy. The body can also use ketones, chemicals created from fat, for energy instead of glucose. (This is, essentially, the whole reasoning behind the keto diet: Without carbs to use for energy, your body will begin to break down fat instead.)

While your body may be able to find other sources of energy, Dr. Karmally warns against cutting carbs out completely—specifically the complex carbs found in healthy foods like fruits and vegetables. “If you do, you’ll be missing out on a whole host of vitamins and nutrients, including fiber, which helps with digestion. That’s why people who go low-carb and increase their fat and protein intake but not their vegetable intake can end up feeling constipated,” she says. To this point, Dr. Karmally says the body can subsist without carbs—it won’t just suddenly shut down on you—but it certainly won’t be in top form: Missing out on the nutrients in fruits and vegetables could lead to more inflammation.

Board-certified sports nutritionist, registered dietitian, and the nutrition director at Trifecta Nutrition Emmie Satrazemis agrees with Gustin that carbs aren’t technically necessary, but like Dr. Karmally, she warns against cutting them out completely. “Even though they aren’t essential for survival, they’re in the majority of foods we eat, including fruits, vegetables, nuts, and seeds. So cutting them out completely would mean missing out on so much nutrition,” she explains, echoing Dr. Karmally’s sentiments.

Satrazemis says there isn’t a hard and fast rule on how many carbs is optimal, but she emphasizes that there’s no need to be scared of carbs or worry they’ll lead to weight gain. “Carbs get a bad rap, but when it comes to maintaining a healthy weight, it’s more about calories,” she says. “If you’re not eating more calories than you need, then you aren’t going to gain weight—even if your diet includes a sizable percentage of carbs.”

What about athletes? Don’t they need carbs? Both Gustin and Satrazemis work with professional athletes and have come to the same conclusion: It depends on the type of sport you do. “If you’re doing something that requires short bursts of energy like sprinting or weight lifting, carbs are a better energy source than protein or fats because they’re stored right in the muscles and are more readily available,” Satrazemis says. “But if you’re doing a more sustained workout, like a long run, healthy fat is an ideal energy source because it’s more low-burning.”

“Carbs get a bad rap, but when it comes to maintaining a healthy weight, it’s more about calories.” —Emmie Satrazemis, RD, CSSD

But both experts point out that, alas, the average person doesn’t have the same nutritional needs as a professional athlete and most people overestimate their fueling needs. But, hey, if you keep hitting a wall during your workouts, you could try adding carbs to your pre-workout snack and see if it makes a difference.

The bottom line is that you aren’t going to feel great if you cut complex carbs out completely—even if you could technically survive. According to Dr. Karmally, “People need to focus less on specific nutrients and more on eating whole, real foods because they are going to get more nutritional benefits that way.”

One major dietary point all three experts agree on: Eating unprocessed, real foods should be the goal no matter what. As Gustin aptly puts it, “It doesn’t matter if your diet is low-carb or high-carb, whatever it is, the key should be eating a 100 percent real food, whole foods diet.”

If you’re trying to figure out which healthy eating plan is best for you, check out this guide. Plus, what you need to know about carb backloading.