Carbs Are Not the Enemy

Many of us probably know people who've lost weight by cutting carbs, but it’s not a sustainable diet, or a particularly healthy one.
avocado toast on a plate
Andrew Cebulka/Stocksy

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Remember when, as a kid, you’d tear off all the couch cushions and play “don’t touch the lava,” aka the carpet? That’s pretty much what everyone who’s trying to lose weight is doing now with carbs, albeit with trendy names like “keto” that don’t sound as lame as simply counting carbs. Whatever you call it, it’s almost as unsustainable as avoiding the living room floor—and, analogies aside, appears to be not very good for you.


Think about it: Paleo dieters have sworn off bread, grains, and even legumes like beans, despite the fact that our ancestors began eating bread about 14,000 years ago, per research in the Proceedings of the National Academy of Sciences. Meanwhile, keto dieters are adamant that carbohydrates are unnecessary for health and cause weight gain. (Though there is some evidence that the keto diet can help people with epilepsy and oncologists are researching if the diet can make certain cancer drugs more effective).

Yes, junk foods like french fries and cookies are high in carbs, but other examples of carbohydrate-rich foods include healthy things whole grains, fruits, vegetables, legumes, and dairy. Many of us probably know people who've lost weight by cutting carbs, but it’s not a sustainable diet, or a particularly healthy one.

So what would happen if your taste buds touched the forbidden lava of carbohydrates? Research suggests that you’d lose weight way more sustainably, run harder, lift heavier, think better, and live longer. You’d also do all that without being so cranky all of the time.

In fact, in the latest meta-analysis to come to carbs’ defense, researchers from Brigham and Women's Hospital and the Harvard T.H. Chan School of Public Health found that people who consume moderate amounts of carbs—or about 50 to 55 percent of total daily calories coming from carbs—had the lowest risk of dying over a 25-year follow-up period. Meanwhile, in one 2018 Nutrients study, overweight people who upped their carb and fiber intake (from plant sources, not junk foods, mind you) lost weight and even improved their body’s ability to keep blood sugar in check. And carbs are an ergogenic aid, or performance-booster, per research in Sports Medicine, improving both endurance and high-intensity interval training performance.


Why your body needs carbs

What all of the anti-carb diets out there seem to ignore is that carbohydrates are your body’s number-one preferred form of energy. In fact, your red blood cells and central nervous system (brain and spinal cord) alone burn through roughly 80 grams of carbohydrates per day. (Hence why you become, uh, irritable as you “adapt” to a low-carb diet.) Sure, you don’t have to eat them to live or put one foot in front of the other—your body can convert fat and protein to energy, too—but we convert carbs way more efficiently and arguably with far better results.

“If we do not get enough glucose through carbohydrate intake, then our bodies will produce glucose from protein through a process called gluconeogenesis,” explains Jim White, a registered dietitian and fitness specialist in Virginia Beach, Virginia. “Over time this process may lend itself to weight loss, however maintaining muscle mass will be a challenge.” He notes that carbohydrates are also vital to your body’s ability to build muscle and, over time, less muscle mass means slower metabolic rates and higher body fat percentages. Basically, the opposite result that people want from a diet.

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Why active people need carbs even more

Low-carb diets can also wreak havoc on muscle health by impairing your ability to work out. Your muscles are what experts call a “glucose sink,” meaning they go through a ton of carbs. “Carbs are the primary fuel for muscle contraction,” explains Kelly Pritchett, an associate professor of nutrition and exercise science at Central Washington University and a certified specialist in sports dietetics. “If you want to perform at a higher level, you need carbs.”


When you train above roughly 70 percent of your VO2 max (the peak amount of oxygen your body can take in and use in a minute), most of your energy has to come from either stored carbs in your liver and muscles, called glycogen, or carbs floating through your bloodstream in the form of glucose, Pritchett says.

While the fitter you are, the harder you’ll have to work to hit your 70 percent VO2 max, most people will reach theirs when doing any high-intensity total-body or compound workouts like rowing, sprinting, or circuits. If you’re too out of breath to carry on a conversation, you’ve likely crossed this threshold—and your body needs carbs to keep your workout moving.

“Carbs also delay fatigue during a workout, optimize endurance activity by helping us maintain glycogen stores, and are important for decision-making during sports like mountain biking or skill-based activities,” she says.

Where you get your carbs matters

Perhaps even more importantly: Carbs don’t occur in isolation. Carbohydrates are simply a macronutrient, and one that comes packaged in foods alongside lots of other nutrients. “Carbs also contain important nutrients and phytochemicals such as vitamin C, potassium, and calcium that we may not find in other fat- and protein-based sources,” Pritchett says.

Of note: Fiber is a carbohydrate, and one that research overwhelmingly shows we need more of for optimal health, including maintaining a healthy weight. One 2015 study in Annals of Internal Medicine found that when people simply increase their fiber intake, they end up losing just as much weight as they do when they go on full-fledged diets. After all, women need roughly 25 grams of fiber per day for good health and men need 38 grams, but most Americans only consume about half that amount, according to the American Dietetic Association. One reason for that is because even though as a society we eat plenty of carbs, most of them aren’t from fiber-rich whole grains or vegetables.


No, more often our carbs are coming from ultra-processed foods. One recent study published in BMJ Open found that foods like frozen pizza and soda make up more than half of all the calories Americans consume in a given day. Previous research from the Centers for Disease Control and Prevention shows that three out of four people in the US get more than 10 percent of their daily calories from high-fructose corn syrup and other refined sweeteners.

That’s not to discount the wonderfulness of donuts and sugary cereals; including them in your diet in moderation is probably a good way to go. Case in point: In 2014, when University of Toronto researchers examined 59 scientific weight-loss articles, including 48 randomized control trials, they concluded that the best diet is the one people can actually stick to over the long term. And the idea of swearing off one food—or one entire macronutrient—isn’t sustainable. Even if you lose a bunch of weight by drastically cutting carbs, as soon as you increase carbs again (and, therefore, total calories), the weight will come back.

Let’s acknowledge for a minute the fact that we’ve all seen plenty of people lose weight by going low-carb. One common scenario is that processed foods were that person’s main source of carbs, and so by cutting carbs they removed these products from their diet—and lost weight. That’s excellent on all counts! But it doesn’t mean that carbs as a macronutrient were the thing standing between this person and their healthiest body.


“When you think of the foods that contain carbs, most people think of desserts, pizza, white pasta, et cetera,” White says. “I think I can speak for everyone when I say these are the foods people love! With that, I think a lot of people have trouble eating these in moderation, so avoiding them altogether is an ‘easy’ solution that usually lends to pretty significant weight loss.

"I have had countless patients tell me that they avoid bread because it makes them gain weight. Could this really be true or is it that most people lack portion control eating these foods, so the excess calories cause weight gain?”

And it’s not just the carb count that matters—it’s what replaces those carbs in your diet, says Scott D. Solomon, professor of medicine at Harvard Medical School and senior physician at Brigham and Women’s Hospital, and author of the recent meta-analysis. “In our study, we found that low carbohydrate intake was associated with higher mortality if the carbohydrates were replaced with animal fat and protein but not if the carbohydrates were replaced with vegetable fat and protein. So it’s not just low-carb or high-carb, but what replaces that carb that seems to matter.”

How to use carbs to hit your health and fitness goals

Per Solomon’s study, getting roughly half of your daily calories from carbs is a good way to go, longevity-wise. For someone eating 2,000 calories per day, that works out to roughly 250 grams of carbohydrates daily. (Each gram of carbs contains four calories, and in case you’re wondering, and each gram of protein also contains four, while fat has nine.) To help you visualize that amount, there are 43 grams of carbs in every cup of cooked spaghetti, 40 grams in a cup of black beans, 16 grams in a cup of butternut squash, and 12 grams in one slice of wheat bread.

Meanwhile, evidence-based guidelines for athletes suggest prescribing grams of carbohydrate per kilogram of body weight. “This amount can be tailored to the individual athlete’s energy needs, and periodized according to phase and type of training,” Pritchett says. “The recommended range is 3 to 12 grams of carbs per kilogram of body weight per day.”

So, for example, if you weigh 150 pounds, that would equate to 205 to 818 grams of carbohydrates. (There are 2.2 pounds in a kilogram.) That’s a huge range, and it’s important to realize that, for a 150-pound person, intake of any more than 200 or 300 grams of carbs per day is typically reserved for elite and professional athletes, according to Pritchett. After all, your body burns through roughly 40 to 60 grams of carbohydrates per hour of exercise.

What’s more, White recommends spreading this intake evenly throughout the day—paired with both protein and fat—to provide a steady stream of energy and nutrients. “Allow for at least half of your carbs to be spread across three meals, and the rest for pre- and post-workout snacks throughout,” he says. And, of course, try to make the bulk of them come from whole food sources: fruits, veggies, whole grains, you know the deal.

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