Low-carbohydrate diets have become very popular in recent years. What do they consist of? Can everyone use them? And can they effectively reduce body weight without any side effects?

What are carbohydrates?

Carbohydrates are one of the three main groups of macronutrients. In the body, the main role is to provide energy – they are important for proper brain and muscle function.

Carbohydrates are divided into:

  • Simple carbohydrates – These are directly absorbed from the digestive system, where they are quickly digested. These include glucose, fructose, galactose. They are found for example in fruits, vegetables, honey and dairy products.
  • Complex carbohydrates – Are more slowly digested. These include starch, pectin and cellulose. They are found in cereal products such as flours, oats, bread, rice and pasta.
  • Fibre – A fraction of carbohydrates that has no energy function, but is very important for our body as it supports digestive functions and has a beneficial effect on intestinal passage. In addition, it normalises blood glucose levels and reduces the absorption of cholesterol.

Types of low-carbohydrate diets

A low-carbohydrate diet is defined as a carbohydrate intake below the established macronutrient intake range for healthy adults.

Among these we can distinguish:

  • Standard carbohydrate diet – 45%-65% of total daily energy or >150g g /day of carbohydrate
  • Low carbohydrate diets – <10%-45% of total daily energy or around 50-150g grams/day of carbohydrates
  • Very low carbohydrate diets – <10% of total daily energy or <50 g/day of carbohydrate (ketogenic diet)


  • Copenhagen diet: carbohydrate 25% of total daily energy
  • Paleo diet: carbohydrate 20% of total daily energy
  • Ketogenic or Atkins diets: carbohydrate < 10% of total daily energy

Benefits of a low-carbohydrate diet 

Many studies indicate that short-term adherence to a low-carbohydrate diet can cause a lot of benefits, including:

  • Effective weight loss;
  • Positive effect on the normalisation of blood sugar and insulin levels;
  • Improved lipid profile;
  • Reduction of risk factors for heart disease;
  • It may improve the appearance of the skin by a reduction in inflammation from refined carbohydrates;
  • An increase in the genetic diversity of the microbiome and, may increase the ratio of Bacteroidetes to Firmicutes

Drawbacks of a carbohydrate-restricted diet

Long-term use of a low-carbohydrate diet can cause a number of disorders, including:

  • Low mood;
  • Problems with memory and concentration;
  • Frequent headaches and dizziness;
  • Fatigue and general weakness;
  • Constipation (mainly due to insufficient dietary fibre supply), nausea, diarrhoea;
  • Risk of nutritional deficiencies;
  • A high risk of the yo-yo effect after ending the diet (gaining the weight back);

With prolonged use of a very low-carbohydrate diet, ketosis can occur. This is a phenomenon that involves the accumulation of ketone bodies – another fuel the body can use for energy.

Is a low-carbohydrate diet for everyone?

The low-carbohydrate diet may be recommended for diabetics, patients with drug-resistant epilepsy and patients with metabolic diseases. It is important to remember that this type of diet must be strictly under medical supervision. For those looking to lose weight, it can be a short-term diet, but unfortunately, it is often very hard to sustain, so we recommend speaking to a dietitian to find the right solution for you.

There are certain groups of people who should not follow this diet. These include:

  • Children;
  • Pregnant and breastfeeding women;
  • People who participate in endurance sports;
  • Vegans and vegetarians;
  • Patients suffering from liver, pancreas and kidney problems.


Many studies show the positive effects of a low-carbohydrate diet. It is recommended, above all, that the diet is varied due to the possibility of nutritional deficiencies. It should be remembered that long-term use of this diet can result in negative effects for some groups. Therefore, it is always best to consult a doctor and registered dietitian before starting this type of diet.

By Martyna Slotwinska, dietetic intern, revised by Reema Patel, Registered Dietitian at Dietitian Fit & Co.


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