Cutting carbs? A dietitian explains 6 reasons you shouldn't

Low-carb diets aren't the only key to weight loss and health.

Amanda Capritto
6 min read

There's a reason the two bottom rows of the food pyramid contain carb-rich foods: They're good for you. 

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"Carbohydrate" was once just a noun used to refer to a macronutrient, but it has now become "carbs," the noun to avoid, to blame and to count, laments Registered Dietitian Ashley Koff, founder of The Better Nutrition Program.  

The prevailing sentiment that carbs are the enemy grew as the number of "hyper processed, refined and fortified" foods grew, Koff tells CNET. Those kinds of foods -- sugary cereals, white bread, candy and the like -- contain empty calories, or calories void of vitamins, minerals and antioxidants. 

Not all carbs are bad, though: "Foods like fruits, vegetables and whole grains, may be high in carbs and calories sometimes, but they are not empty," Koff says. "They deliver fiber, protein, B vitamins and other nutrients."

People often turn to low-carb or keto diets as a quick way to lose weight -- keto diets are known to induce rapid weight loss in the first few weeks, but it's not always sustainable. For one thing, everyone is different and won't see the same results on a low-carb diet, Koff explains, and secondly, it's hard to keep up with a carb-free diet long-term. 

Koff recommends that anyone considering carb reduction or elimination should work with a qualified professional and discuss short- and long-term benefits. If you wonder if your current carb intake is too high, Koff recommends keeping a food journal and sharing it with your doctor

With that, here are six reasons cutting carbs might not be the right approach for you. 

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Healthy carbs include whole-grain bread and pasta, rice, beans, peas, legumes, starchy vegetables and fruits.

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You might be missing out on key nutrients

Many carb-heavy foods are rich in essential vitamins and minerals -- yet there's a persistent misconception that "carbs" equal "bad." 

Koff explains that the reality is quite the contrary: "Carbs come in many forms," she says. "Better or 'healthy' carbs provide value by bringing critical nutrients into the body [such as] fibers, minerals, vitamins like magnesium and B12, and antioxidants."

These healthy carbs support metabolism, digestion and immune health, Koff says, explaining that they act as building blocks for healthy bones, muscles, cartilage, skin and even blood. 

When you completely cut carbohydrates out of your diet, you could put yourself at risk for nutrient deficiencies if you don't replace those nutrients with other food sources. For example, Koff points out that about 70% of Americans don't get enough magnesium, an important mineral that cells need to "turn off" stress. 

"When you reduce or cut out carbs completely, especially grains and beans, you will further reduce your intake of this essential nutrient," Koff says. "Therefore, your total nutrition plan must include other sources of this nutrient."

Read more: How to read the new 2020 nutrition facts label


When checking the nutrition label for carbs, pay more attention to added sugars (new on nutrition labels in 2020), which is more indicative of how healthy a food is.

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You may not get enough fiber

Fiber is one nutrient you may not consume enough of if you don't eat carbs. Whole grains, fruits and vegetables, especially starchy ones, are some of the greatest sources of fiber. But they also happen to be high in carbohydrates. 

Fiber plays key roles in digestion, heart health and gut health, Koff says. Research backs this up: Studies show that people who eat more fiber have a lower risk of developing cardiovascular disease and tend to have more beneficial bacteria in the microbiome.

Fiber can also help you feel fuller for longer periods of time, which is helpful if you are trying to lose weight

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Fiber is found in starchy vegetables like carrots, as well as other vegetables, beans and whole grains.

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Carbs are good for your brain

Carbohydrates are your brain's preferred source of energy. Scientists estimate that the brain consumes roughly 120 grams of carbohydrates every day and that your brain accounts for roughly 20% of your total energy (calories) burned each day

When you first start a low-carb diet, you may experience brain fog, mental fatigue and mood swings because your body's primary fuel source suddenly disappeared. Once your body adjusts, those symptoms should subside, but those initial effects are part of the reason why low-carb diets are so hard to stick to. 

Koff says that many people confuse the role of stimulants like caffeine with the role of carbohydrates: Caffeine and other stimulants provide short-term bursts of energy, whereas healthy carbs supply your brain with what it needs to perform its many functions and give you long-term energy. 

"It's important to choose healthy carbs, as the quality of these carbs is the real factor in determining not just what the brain gets to run, but how it and the rest of the body will use those carbs and what the outcomes will be health-wise," Koff says. 

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Carbs are brain food. 

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Carbs can help you build muscle

Protein often claims the fame when it comes to bulking up, but carbs are just as important: When you eat carbs, your body converts some of them to glycogen, a storage form of carbohydrate that stockpiles in your muscles. Your body uses glycogen when it needs a quick energy boost or it isn't getting enough energy from the glucose in your cells. 

Glycogen really comes in handy when you're lifting heavy weights in the gym: Without enough stored carbohydrates, you might fatigue too quickly or feel weak. This is where the practice of carb-loading before weightlifting competitions and long-distance races comes from -- it's said to maximize muscle glycogen stores in advance of performance

Additionally, carbs can help your muscles repair themselves quicker after tough workouts. The general consensus is that eating carbohydrates as soon as possible after exercise can "maximize muscle glycogen replenishment" and limit post-exercise muscle damage. 

Read more: Body recomposition: How to lose fat and gain muscle at the same time

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Lack of carbs might be the reason your fitness has plateaued

If you notice your fitness gains halting, you may benefit from analyzing your diet. Carbohydrates provide your body with quick energy: It's the first macronutrient used for fuel, and it's the easiest to release from storage. 

Dietary fat and protein give your body energy, too, but your body doesn't utilize either as efficiently as it does carbohydrates, especially when you first switch to a low-carb diet. 

"Carb intake should be determined on a personalized basis," Koff says, but "practitioners who work with athletes and very active individuals will often determine the nutrient needs to support health and performance cannot be met without carbs because of their role in energy metabolism, muscle formation and recovery, digestion, mood and sleep."

So if you feel as if your performance in the gym has plateaued, you may simply not have enough readily available energy for your body to perform the tasks you want it to perform. Adding healthy carbohydrates, such as oats, quinoa or fruit, to your diet can help. 

If you feel like you often feel weak, slow or generally poor at the gym, you may also want to pay attention to your overall calorie intake. If you aren't eating enough to support your fitness routine, your body won't have enough energy to get stronger, faster or more fit.


Eating healthy carbs before and after workouts can support your efforts in the gym.

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Cutting out food groups can lead to disordered eating

While Koff says no one should generalize disordered eating and eating disorders, cutting out food groups has been associated with disordered eating habits.

This is particularly true with regard to orthorexia nervosa, or an obsession with healthy eating that progresses to the point of a disorder. "Orthorexia nervosa is perhaps best summarized as an obsession with healthy eating with associated restrictive behaviors," one study states

Carbohydrate is not the sole macronutrient related to disordered eating, but it's worth calling out that complete elimination of any food group can contribute to the development of a poor relationship with food. 

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The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.