Dr Araz Rawshani

Calories and body weight


Calories in, Calories Out – Is 1 Calorie Always 1 Calorie?

For several decades it has been said that 1 calorie is always 1 calorie. It does not matter whether the calories come from carbohydrates, fats or proteins. For those who want to lose weight, eat fewer calories. This theory comes from the concept of energy balance, which is a simple concept. Energy balance is simply the difference between the number of calories we eat and the number of calories we consume. If our food contains more calories than we consume, we have a positive energy balance and then we gain weight. If our food contains fewer calories than we consume, then we have a negative energy balance and then we lose weight. In recent years, many scientists and laymen have come to question this theory and instead emphasize the importance of the composition of the food. In Sweden, the LCHF movement gained strong support and this movement claimed that the composition of the food was more important than the number of calories. The strongest message of the LCHF movement was that carbohydrates are especially unfavorable for those who want to lose weight. Today, therefore, there are two competing theories regarding what is most important for losing weight:

  • Calories in, calories out (Energy balance): according to this theory, it does not matter how much fat, protein, and carbohydrates you eat; the important thing is instead the number of calories. According to this theory, it is important to count calories.
  • The carbohydrate insulin model: according to this theory, the composition of food is important; it is considered that carbohydrates are worse calories than fat, and anyone who wants to lose weight should eat fewer carbohydrates and more fat. According to this theory, one does not need to count calories.

The big question is: does the composition of the food matter?

Carbohydrate insulin model and low carbohydrate diet (LCHF)

There is no doubt that energy balance is extremely important for our body weight. Energy balance is thus the difference between the number of calories we eat and the number of calories we consume during the day. We consume energy when we sit still (because the body has a combustion even when we are completely still) and when we move (then combustion increases). Since the energy balance is crucial, limiting the number of calories we eat should lead to losing weight and this is true. If you eat fewer calories than you consume, you lose weight. The problem is that diets with caloric restriction (diets where you eat fewer calories) do not manage to give rise to long-term results.

Eating fewer calories thus gives a quick weight loss at the beginning, but then you usually gain weight again. This is mainly because you start eating too much again (read Why is it so difficult to lose weight?). However, other researchers believe that calorie restriction is not a good method for losing weight, but instead one should focus on changing the composition of food, which means changing the proportion of carbohydrates, fats and protein. The most popular of such diets is LCHF (low-carbohydrate diet), which is about eating much more fat and much fewer carbohydrates. There has been a lot of research on LCHF (low carbohydrate diet) and the results have resulted in the Carbohydrate Insulin Model. There are good studies that suggest that it is easier to lose weight if you eat LCHF (low-carbohydrate diet), compared to eating less fat (low-fat diet). Here is a diagram showing the results of a well-known study:

According to the carbohydrate insulin model, carbohydrates are particularly bad for us. The theory says that processed carbohydrates with a high glycemic index (carbohydrates that give a sharp rise in blood sugar) lead to hormonal changes that cause us to gain weight, no matter how many calories you eat.

According to the Carbohydrate Insulin Model, carbohydrates cause hormonal changes which in turn lead to storage of carbohydrates in the form of fat, becoming hungrier and burning less energy at rest.

David Ludwig, a researcher at Harvard University, believes that there is convincing evidence for the carbohydrate insulin model.


Ludwig emphasises the following:

  • In animal studies, it has been shown (clearly) that the composition of food (percentage of fat, carbohydrates and protein) affects metabolism and body composition, regardless of the number of calories that animals eat.
  • Studies investigating human behavior show that weight loss is greater on diets with Lower carbohydrate content (low-carbohydrate diet), compared with diets with lower fat content (low-fat diet).
  • Studies in humans show that carbohydrates have a worse impact on our metabolism.

Proponents of the carbohydrate-insulin model, which includes those who advocate LCHF, argue that those who want to lose weight must try to reduce their carbohydrate intake, especially the intake of carbohydrates with a high glycemic index. These scientists believe that emphasis should not be placed on the number of calories.

Our diets changed dramatically in the 1970s

Those who advocate the carbohydrate insulin model believe that despite trying to get people to eat less food and exercise more, the population has gained weight and the incidence of diabetes has increased dramatically throughout the world, including Sweden. It is believed that carbohydrates are particularly prone to be stored as fat in the body. When the carbohydrates are stored as fat, less energy is available in the blood and then we get hungry, which leads to us eating too much.

Insulin is considered to have a key role in this context. The pancreas (pancreas) releases insulin into the bloodstream when we eat food with carbohydrates. Insulin causes the following effects:

  • Blood sugar (glucose in the blood) drops because insulin stimulates the body’s cells to absorb sugar from the blood.
  • Insulin leads to a cessation of fat breakdown. If you fasten, no insulin is released and then we break down fat, whereby ketones are made and put into the blood and ketones can be used as energy.
  • Insulin results in glucose (sugar) being stored as fat in the fat tissue.

Read more: Metabolism: insulin, carbohydrates, fat and protein

We also know that people with type 2 diabetes who receive treatment with insulin gain weight when treatment starts. People with type 1 diabetes have a lack of insulin and lose weight; when they start treatment with insulin, they gain weight again.

Glycemic index

The glycemic index is a measure of how strongly the blood sugar rises by the food. Mate with a high glycemic index provides a sharp rise in blood sugar, while food with a low glycemic index provides a less pronounced rise in blood sugar. All fast carbohydrates and starches have a high glycemic index (e. g. potatoes, sugar, rice, pasta, etc.).

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  1. Ludwig et al (2018): The Carbohydrate-InsulinModel of Obesity Beyond “Calories In, Calories Out”, JAMA Internal Medicine