Can You Survive Without Carbs? | Ask The Dietitian

Trinh Le, MPH, RD
by Trinh Le, MPH, RD
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Can You Survive Without Carbs? | Ask The Dietitian

Are you carb-curious? The popularity of low-carb, ketogenic and other Atkins-style diets are fueling an intense fascination around this macronutrient. As a dietitian and self-professed science junkie, I feel the need to deepen our understanding of this topic so as to not glorify or demonize a nutrient (unless it’s well-deserved!). So, why are carbohydrates so important? Are they really essential in the diet? Read on to find out.


Carbohydrates achieve staple status in our diet because they supply a magical thing called glucose, a sugar. (OK, it’s not magic, just science.) If you weren’t automatically transported back to biology, let me explain.


Our body runs on calories, and it gets those calories by metabolizing carbohydrates, fat and protein from our food. Since our body smartly spares protein for rebuilding and repairing tissue, carbohydrates and fat are by far the fuel of choice. While every cell is capable of burning glucose  for energy, the same is not true for fat.


Our brain and red blood cells rely on the plentiful glucose in carbohydrates. Through gradual adaptation, the brain can learn to use fat in the form of ketone bodies, but our blood cells will always rely on glucose. In fact, our body fights really hard to keep our blood glucose levels within a narrow window. Once you dip below the minimum threshold of 20mg glucose/dL of blood you risk slipping into coma or having a seizure. This biological fact is partly what drives the daily recommendations for carbohydrates by major health organizations (see below).



Carbs make up a large percentage of the U.S. food supply, contributing anywhere from 50–60% of calories since 1910. This makes sense given that the world’s staple crops are carb-heavy. These include cassava, corn, plantain, potato, rice, sorghum, soybean, sweet potato, wheat and yam. Fruits and vegetables, the foundation of a well-balanced diet, also contain carbohydrates. Even dairy contains milk sugar, which is a carb. Most modern societies base their diets on carbohydrate-rich foods.


Here’s where the argument that carbohydrates are essential starts to crumble:


The healthy human body is fully capable of reforming the amino acids from protein into glucose. Even the breakdown of fat for energy yields the tiniest bit of glucose. If an individual is eating enough calories, even if those calories are mostly from fat or protein, that person can still satisfy the glucose needs of their brain and blood cells and maintain their blood glucose at a normal level.


Nutrition science defines a nutrient as “essential” if we must get it from the diet because our body can’t make enough of it to meet our needs. Deficiencies in protein, essential fats (linolenic and linoleic), vitamins and minerals all match up to an impairment or disease. This same phenomenon doesn’t exist with carbohydrates.


Reach outside the literature, and it’s easy to obtain anecdotal evidence of people who survive on very low-carbohydrate diets. (Note that we’re not taking into account sustainability or personal happiness when subsisting on these diets.)

  • The Atkins diet advocates followers eat as little as 20 grams of carbohydrates per day! To give you an idea of what this means: 20 grams is the amount of carbs in 1 small (6-inch) banana.
  • The classic ketogenic diet is 80–90% fat. It was originally used as a therapy for epilepsy but is now gaining popularity for use in weight loss.
  • The traditional Inuit diet, which is what the natives of northern Canada subsisted on for many years, is empty of refined sugar and grains. Instead, there’s plenty of fresh seal, walrus and other marine life on the menu. A 1980s study of that diet found that it contained, on average, 23% calories from protein, 39% calories from fat and 38% calories from carbohydrates.



Carbohydrates (including fiber) don’t necessarily make the cut as “essential” nutrients, but they are very important. Eliminating carbs completely from the diet is not only impossible, it’s impractical. Fruits, vegetables, whole grains and dairy all contain carbs and are foundational to a healthful diet. When it comes to choosing how low-carb you should go, keep in mind that:

  • Everyone responds differently to varying levels of carbohydrates. Our bodies are unique, so what works for one person may not work for another. The key is to do some research, then experiment to figure out what works best for you. Enlisting expert guidance from a doctor or dietitian can make this process easier.
  • The best diet is one that can be followed over time. Consistency is key to a healthy lifestyle. Setting yourself up with a plan that allows 20 grams of carbs per day may not be the best way to achieve this. A balanced diet is one that allows flexibility for you to fit in foods you enjoy regardless of carbohydrate content.
  • “Low-carb” can be a healthy lifestyle. Most low-carb diets don’t go as low as you think, hovering around 35–40% of calories from carbohydrates. For many, the term “low-carb” has become synonymous with eating less refined carbs and added sugar and eating more fruits and vegetables. Needless to say, I’m on board with that!

About the Author

Trinh Le, MPH, RD
Trinh Le, MPH, RD
Trinh is a registered dietitian by day, blogger at Fearless Food RD by night. She loves helping folks develop a better relationship with food, which includes lots of cooking, eating and learning about nutrition. When she’s not snapping mouthwatering shots of (mostly) healthy food, you can find Trinh HIIT-ing it at her local gym. For more, connect with her on FacebookInstagram and Pinterest.


15 responses to “Can You Survive Without Carbs? | Ask The Dietitian”

  1. Avatar BadKarmaGhost says:

    A cancer cells’ usual fuel supply is glucose.

    • Avatar Mary1254 says:

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  2. Avatar Biological Science says:

    Cancer is caused because of the protein cyclin unable to send signals to stop growing. All cells grow because of nutrients; and you guessed it, carbohydrates are nutrients! So atop portraying a nutrient as a terrible part of someone’s diet.

  3. Avatar Ro says:

    Everything you say is true though you need to delve a little deeper into the science.
    The body converts all ingested food into a form of glucose before any food source can be utilized by the body with the exception of simple sugars found in sweet and highly refined “food”. These products are not strictly food but could be defined more accurately as chemicals or empty calories devoid of any nutrition.
    Humans were not originally designed to consume grains ( hence the reason for so many food intolerances) and can successfully survive and flourish without the addition of grains in the diet.
    Many people don’t realize that all vegetables and fruit are carbohydrates (complex carbohydrates) and these are the only carbohydrates our bodies need to function healthily.
    Big industry promotes the ingestion of simple carbohydrates and because they have no nutritional value, synthetically produced vitamins and minerals are added so these products can be marketed as “healthy food”. This, of course creates the mutli-vitamin and mineral supplement industry which is completely unnecessary if we eat real food.

  4. Avatar Christine Rogers says:

    Not quite sure why the author has the lense that modern American diets are healthy. Seems odd to refer to the average diet of a population that is morbidly obese on average as a benchmark for health or happiness.

    • Avatar George says:

      probably because average obese population eat way too much processed food with unhealthy lifestyle. They are not even on “average diet”.

    • Avatar Oli Ohlson says:

      “Lense” is an archaic variant spelling that is no longer in use. Read more books and get off instagram, idiot.

  5. Avatar Lin Sp says:

    Some things I’ve learned since being diagnosed with Type 2 diabetes:

    Low carb does not mean 0 grams of carbs.

    Atkins’ 20 grams/day of carbs is only for the first two weeks of following their plan. Then you’re supposed to gradually increase the carbs until you find the level that allows you to continue to lose weight, since that’s the goal of the plan.

    Many people whose metabolisms don’t process carbs well due to metabolic syndrome, diabetes, insulin resistance, do very well following a low carb food plan, once they figure out how many grams of carbs/day works with their specific metabolism.

    People whose metabolisms work properly can do well on pretty much whatever food plan they choose to follow. So, people who say, “I did this and it did that, so everyone else should do what I did to get my result,” are pretty much wrong. That’s only true if the people they’re recommending it to have the same metabolism as you. Otherwise, your prescription may be totally wrong for them.

  6. Avatar Mark Spaulding says:

    Being able to “survive” without carbs doesn’t make them not essential. We can “survive” without food for numerous days. A Human can go for more than three weeks without food (Mahatma Gandhi survived 21 days of complete starvation).
    So, as you can see, we can also “survive” without protein & fats. So, does that mean Protein & fats aren’t essential now? Didn’t think so.
    Just because the human body can “survive” without carbs by converting BCAA into glucose doesn’t make carbs non-essential. It just means your Body is smart and can adapt to environment, emergency situations, etc. Carbs are essential. Nothing anyone can say will change my mind on this subject.

    • Avatar Larry Hoffman says:

      Appreciate your open mindedness…….However, the human body will die from malnutrition without essential fats and amino acids (of which we can’t produce, hence being essential). You could live your entire life expectancy without intaking any meaningful amount of carbohydrate.

    • Avatar Tom says:

      Carbs are non essential. Fat and protein are NOT. You must have fat and protein, or you die. You don’t need carbs. The liver can convert fat into glucose. Some cells do need trace amount of glucose, but you can get that from non-starchy vegetables quite easily. 100 grams of cabbage does it. You would also get enough by eating a few eggs, which contain trace carbs. Humans eat far too much carb, and our health is taking a toll.

  7. Avatar dexter62 says:

    i have type 2 diabetes, seems I’m always up against the wall when I get going good on a diet , then the sugar cravings drive me nuts along with the thirst, I started the keto diet about a week ago, and thought I’ve been on almost every other diet, this time the cravings were manageable (easily) THE THIRST HAS GONE AWAY, although I drink a lot of lemon water throughout the day, and the hunger seems to be less formidable than it had been on other diets, not much change yet on the scale but I don’t think i’ll be able to achieve ketosis for awhile yet, but just being able to the normal negative components of dieting this time tells me I’m on the right path for my body and metabolism.

    • Avatar Tom says:

      I was diagnosed with A1c of 10. Now am 5 after 8 months on keto. The sugar cravings don’t last forever :). Consult your doctor of course, but it worked for me. They didn’t want me to do it but I didn’t want to take drugs. I no longer require insulin or medication. Down 55 lbs. It was pretty much all diet since I only started exercising recently. If you’re interested, I highly recommend the videos by Dr. Jason Fung.

  8. Avatar Lj Thomas says:

    I think Trinh Le’s article here is a relatively refreshing “voice of reason”. There is so much conflicting dietary advice being thrown in our faces daily by high carb (plant based) versus low carb (ketogenic) wellness advocates that neither side is helping . This constant tug-o’-war is only engendering mass confusion among the general public in terms of what constitutes a healthy diet for both weight loss and general well-being. The bottom line for me is an eating regimen that is sustainable as a lifelong tool. It has to include foods which I enjoy eating and which allow me to live a fulfilling social life. For me, any diet that vilifies fruit, for example, is not one that I can live with. A low carb diet of 1500 calories per day allowing up to 90 grams of carbohydrate from natural organic sources of produce has helped me lose 138 pounds in 2 years. Now at age 67, despite having hypothyroidism and a lifelong history of obesity and genetic predisposition to weight control issues, I have maintained this weight loss for 20 years, and unlike many of my family members and closest friends, I have had no issues with diabetes, hypertension, heart disease, cancer, COPD, sleep apnea or any other age or obesity related condition. I sincerely wish that everyone is successful in finding what works best for them, and I respect everyone’s individual differences and preferences.

  9. Avatar Tom says:

    The cells in the body that require glucose can be satisfied by trace
    carbs you get from eating non-carb heavy foods. 100 grams of cabbage is
    plenty. that’s 80 calories, mostly sugar, and will feed your red blood
    cells just fine. There is no minimum requirement for carbohydrate intake, and most modern people eat *way* too many. The brain does require glucose, but the liver can synthesize glucose from fat just fine.

    We didn’t evolve metabolizing grains, we evolved on fat. So it’s little wonder that metabolic diseases are becoming the norm since most people rely on grains.

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