Why calorie counting is a flawed system
by Lucia Stansbie
As the new year starts many people decide to embark in a new with the goal of losing weight.
The first idea that springs to mind is to limit calories and start doing calorie counting – there are flaws in this approach to diet, mainly because the calorie system is flawed.
A calorie is a unit of measure of energy. Very specifically, it is the amount of energy that is required to raise the temperature of one mL, (which is also one gram), of water by one degree Celsius. During the late 19th Century, scientists started to be interested in the amount of calories in different foods. Using a device called a bomb calorimeter, a known amount of food which has had its water content evaporated, was placed in a container surrounded by a known amount of water. The container was sealed, oxygen piped in, and the food ignited. From the rise in temperature of the water, the calorie content of the food was calculated. Using this device, a chemist called Wilbur O. Atwater determined the calories in 1 gram of fat, carbohydrates and protein (9-4-4), and consequently calculating the total calories of a specific food based on its content of fats, carbohydrates and proteins.
When referring to foods we talk about Kcalories – the energy required to warm up a kilogram of water by 1 degree Celsius.
The flaw in these methods is that not a single piece of food is equal to the other. It is considered that a medium egg will have 66 kcal but is easy to understand that all medium eggs are different in size and in yolk content. Being yolk mostly fat will change the total amount of kcalories in the egg.
Calorie counting system doesn’t also consider how foods are processed and absorbed by our body. Our digestive system doesn’t extract every single calorie, and this depends of the kind of food and our gut microbiota composition. Less calories are extracted from whole foods– for example the kcal content of whole almonds can be up to 30% lower than what is stated on the package. Some strains of microbes in the gut can increase extraction of calories from foods, while some pathologies can inhibit nutrients absorption.
Another concept to be mindful of is the thermogenic effect of foods, meaning the amount of energy required to process and digest them. Again whole foods are harder to break down and will required more calories to be processed than processed foods that are more absorbable and need minimum effort to be digested. Another example are proteins that have a higher thermogenic effect that carbs, as those are harder to break down requiring the body to produce more enzymes in order to digest them.
Considering that the Kcal we believe food has is approximative and that we don’t know how much or little calories our body extracts from each morsel of food, you will realise that the idea of calories in-out has little relevance when applied to weight management.
A better approach is to consider diet holistically, and as studies confirm focusing on wholefoods that support the microbiota and the metabolism without any obsessive calorie counting and label reading.