Can we live without sugar?

Carbohydrates are one of the three macronutrients, along with proteins and fats, that are essential for a healthy diet. They provide energy for the body and fuel for the brain, and perform a variety of other functions.
Carbohydrates are found in many types of food, such as bread, fruit, vegetables, cereals and dairy products.

So is it possible to live without sugar?

Before we know whether it's possible to live without sugar, let's look at its role in the body.

The role of sugar in the body

As soon as it enters the bloodstream, glucose can be immediately converted into energy or stored as glycogen in the liver and muscles. This reserve varies from person to person, but on average, an average-sized man weighing 70 kg can store around 100 grams of glycogen in his liver.

When carbohydrate consumption ceases for several hours, liver glycogen is broken down into glucose and released into the bloodstream to maintain blood sugar levels, thus preventing any excessive fall in blood sugar levels. Unlike glycogen stored in the muscles, which remains available locally to meet muscle energy needs and cannot be released into the bloodstream to fuel other cells.

Glucose is the brain's main fuel, essential for optimal functioning and maintaining vital functions such as breathing and transmitting nerve signals. The brain consumes around 20% of our daily energy intake.

Lipids: the body's other fuel

Glucose is not the only fuel the brain can use. The brain can use ketones to meet a large proportion of its energy needs.

After a period of 24 to 48 hours without carbohydrate intake, the body's glycogen reserves are gradually depleted. It is at this point that the liver intensifies its production of hydrophilic compounds known as ketones, resulting from the breakdown of fatty acids. These ketones are generated from the fats consumed or from the body's lipid reserves. They can then cross the blood-brain barrier to provide an essential source of energy for the brain.

Studies have shown that for some people following a strict ketogenic diet, characterised by low carbohydrate consumption (such as sugary foods, bread, pasta, rice, juices, etc.) and high fat content (such as red meat, oily fish, cheeses, butter, avocados, nuts and seeds, etc.), ketones can provide up to 50% of their basic energy requirements and even up to 70% of the brain's energy needs.

The ketogenic diet has been around for almost a century, but has been enjoying renewed interest since the mid-1990s. It is based on a significant reduction in carbohydrate intake, accompanied by a substantial increase in fat consumption, which stimulates the endogenous production of ketone bodies.

However, for individuals used to a diet rich in carbohydrates who choose to remove sugar from their diet, a period of adaptation is necessary. The brain, which is used to functioning mainly on glucose, will continue to draw on body reserves for some time. Once the body has adapted to a very low-carbohydrate or even carbohydrate-free diet, the brain begins to use ketones to meet a large part of its energy needs, while the liver produces the necessary amount of glucose to meet the rest of the requirements, as indicated in a study published in 2017.


Caution is advised when considering the ketogenic diet, as it can cause various side effects, some of them serious. These include intense thirst, nausea and abdominal pain. In addition, the state of ketosis induced by this diet requires a significant increase in the intake of water and essential minerals such as calcium, potassium and magnesium.

Eliminating sugar from the diet also entails risks. Indeed, it is virtually impossible to achieve such a goal, given that most foods, even in small quantities, contain carbohydrates. A draconian diet of carbohydrate restriction would mean giving up vegetables, fruit and certain other foods that are beneficial to health. Despite their simple sugar content, limiting their consumption does not seem wise.


It is not impossible to live without sugar, but it is essential to follow such a diet carefully and to complement it with a balanced diet in order to avoid any risks, while controlling any undesirable effects for the patient or sportsperson concerned.

>> Don't hesitate to consult our other articles, in particular "Ketogenic diet for sports people".


Bibliography :
Courchesne-Loyer, A., Croteau, É., Castellano, C., St-Pierre, V., Hennebelle, M., & Cunnane, S. C. (2016). Inverse relationship between brain glucose and ketone metabolism in adults during short-term moderate dietary ketosis: A dual tracer quantitative positron emission tomography study. Journal Of Cerebral Blood Flow And Metabolism, 37(7), 2485-2493.
Sanchez, S. (2021, December 21). Can we live without sugar? - Acai Delight. Acai Delight.
Chief Scientist of Quebec. (2021, March 22). Can't live without sugar? Wrong - Chief Scientist of Quebec. Chief Scientist of Quebec.
De Saint-Martin, A., & Bürger, M. (2013). The ketogenic diet: a diet of extremes? Médecine des Maladies Métaboliques, 7(2), 139-143.
Schlienger, J. (2019). From sugar delight to sugar crime. About a public health controversy. Médecine des Maladies Métaboliques, 13(2), 156-163.
Porta, N., Vallée, L., Boutry, E., & Auvin, S. (2009). The ketogenic diet and its variants: certainties and doubts. Revue Neurologique, 165(5), 430-439.
home. (n.d.). CHUV.

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