Healthy eating


Cake & Ice cream

The low-carb show 1/4

Out of the many diets nowadays there are a lot that propose to limit your carbohydrate intake and thus eat more of the other macronutrients, fat and protein. All these diets see carbohydrates as the dietary supervillain that makes us sick and overweight, but is there actually any truth in this?

A big evolutionary step in the history of the world happened when plants gained the ability of photosynthesis. With this process plants use the energy from the sun to convert carbon dioxide and water into carbohydrates. Inside the plant’s cells the most basic carbohydrate, glucose (a simple sugar molecule), is linked into chains and when these chains gather in large quantities inside the plant’s cell, they form starches. These starches are used by the plants as an energy reserve and allowed other organisms that don’t have the ability for photosynthesis, like humans, to flourish, because they now could eat these plants as their source of energy. Humans use these carbohydrates as their main source of energy and for example our brain is specifically dependent on glucose, which is derived from the breakdown of carbohydrates, for energy and normal functioning. The adult brain requires some 120 grams of glucose on a daily basis.

When we eat food with carbohydrates the enzyme amylase, which is present in our saliva and intestines, breaks these carbohydrates down into glucose molecules which are then absorbed into the bloodstream. When the level of sugar in the blood goes up, the pancreas releases the hormone insulin. You can see insulin as the key that opens our cells and allows the sugar in the bloodstream to enter the cells, providing them with energy. Insulin is also required for the absorption of amino acids into the cells to create new proteins, and thus insulin is seen as the main body building (anabolic) hormone.

Our muscles and liver have the ability to store any glucose that is not directly needed by our body cells in the form of glycogen, similar to how plants store their energy reserves. Adult bodies are able to store some 500 to 1000 grams of glycogen. In between meals the liver breaks this glycogen down again into glucose which it releases in the bloodstream. In this way our cells are provided with a constant source of energy between meals and have a source of energy for sudden strenuous activities like sprinting. So how came it about that all these diets shun carbohydrates, which enable the body to adapt to a diverse range of situations.

The main idea behind all these low carbohydrate diets is to make our bodies switch from using its preferred fuel source carbohydrates, to burning fats for energy. They believe that carbohydrates are uniquely fattening because carbohydrates raise insulin levels and in this way cause fat to be stored excessively in the body, leading to obesity. There does not exist any good evidence for such an association between the actions of insulin and the excessive accumulation of fat in the body. The fact that although protein does not raise your blood sugar, it significantly raises your insulin levels, is disregarded.

It is also often mentioned that there is some sort of a ¨metabolic advantage¨ with low carbohydrate diets (1), which would mean that you burn off many more calories a day extra. This hypothesis goes against basic biology and is proven to be false (2,3,4).

The first one that popularized a low carbohydrate diet was William Banting, an English undertaker who wrote a booklet ¨Letter on corpulence, addressed to the public¨ in1863. In the booklet Banting told of his personal experiences with trying to lose weight. His booklet remained popular for years and his name is still sometimes used as a verb ¨to bant¨, which is still sometimes used to say someone is on a low carbohydrate diet.

Several others have come up with similar diets after the initial booklet from William Banting but the idea of a low carbohydrate diet to lose weight really came back in the spotlight in 1972 with the release of the book ¨Dr. Atkins diet revolution¨ by the cardiologist Dr. Robert Atkins. His low carbohydrate diet came eventually to be known as the Atkins diet. After 20 years his book was reissued as ¨Dr. Atkins new diet revolution¨, which basically promoted the same diet. This book became backed by a big marketing campaign, the bestselling diet book in history.

Many others were inspired by the success of the Atkins diet book and came up with their own versions of the low-carbohydrate diet. Some better-known examples are the South beach diet & The Zone diet which also both limit the intake of carbohydrates.

Another example is Paleo diet, which tells us to eat as our Palaeolithic ancestors allegedly did. The belief that the European Palaeolithic diet consisted for a large part out of animal foods has been countered by recent findings. These findings suggest that the use of vegetables and starches was widespread in Europe at least as far back as 30.000 years ago. Even the Neanderthals ate a variety of plant foods and possibly cooked them for easier digestion, as starch grains have been found as deposits on the teeth of their skeletons.

The most extreme form of a low carbohydrate diet is the ketogenic diet. This diet was devised by Dr. Russel Wilder in 1924 as a treatment for epilepsy in children that couldn’t be controlled by medication. Before the advent of injectable insulin this diet was the only treatment for diabetes. Earlier research had shown that fasting was an effective treatment for seizure disorders. Fasting has off course a very limited applicability in fast growing children and Wilder discovered that when you would get most of your calories from fat, and thus severely restricting carbohydrate and limiting protein intake, the body would go into a metabolic state called ketosis. This state of the body was effective in reducing the frequency of the seizures for about a third of the patients. Only the short-term effects of this diet have been studied, with mixed results, and we don’t know which will be the long-term effects(5). Adherence to the diet is also a problem because Wilder´s ketogenic diet, also known now as the classic ketogenic diet due to the many variants that sprung up, aims to get about 90% of calories from fat and many participants in studies on the effects of the diet dropped out prematurely because of poor tolerance to the diet. The short-term side effects are diarrhoea, constipation and vomiting.

When the body is deprived of carbohydrates, it goes into ketosis, a metabolic state in which the body uses ketone bodies as its main energy source. Ketone bodies are derived from the breakdown of fat, which happens constantly in our bodies but what we call ketosis is when the use of this energy source is greatly increased and becomes the main source of energy. Ketosis is an adaptive state that gave our ancestors the ability to use their fat reserves in times when there was no food or only very low energy food available. So, you could say that the first ketogenic diet was actually famine. When the body goes without food or carbohydrates for some 24 hours the liver’s glycogen reserves become depleted and the production of ketone bodies gets ramped up. Fat cells get broken down into fatty acids and glycerol, which is the backbone onto which the fatty acids are attached. Triglycerides consist of 3 fatty acids and a glycerol backbone. The liver will turn these into ketone bodies which are then used as energy. The brain cannot run on ketone bodies alone and still requires some glucose as fuel. This glucose is made from the glycerol backbone and in the first few days of going without food the body uses a process called gluconeogenesis to make extra glucose. During gluconeogenesis, the body breaks down protein out of muscle tissue into the individual amino acids of which most can be used to create glucose. After a few days of going without food or carbohydrates the production of ketone bodies reaches a point where they are able to provide most of the energy needed for the brain and the breakdown of proteins comes to a halt. In this way ketosis makes sure the brain is provided with energy while the vital proteins are spared.

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