The truth about calorie counting for weight loss

What is a Calorie?

Anyone who has ever tried a fad diet, or any weight loss diet, has most likely come across calorie counting as a method to lose weight. Counting calories to lose weight is much more complex than what many fad diets may want you to believe. But what is the truth about calorie counting for weight loss?

Firstly, it may be useful to understand what exactly a calorie is. In fact, a calorie is a unit of measure that we use to calculate energy. An object called a bomb calorimeter measures how much energy is contained within a certain food. Another unit of measure which you may frequently see on food labels is kilojoules. One calorie (1 kcal) is essentially equal to 4.2 kilojoules (4.2 kJ).

A Complex System

Calorie counting is based on a system called the Atwater system which dates to the 1800s, this was a method to estimate the number of calories in a specific amount of food based on the total amount of grams of macronutrients (carbs, protein, and fat) that it contains. However, these numbers do not provide information about how much of each macronutrient our bodies can either digest or absorb. Nor do calories tell us how certain foods affect our blood glucose levels for example.

If we take the example of nuts, we can see that calorie counts are not always a reliable piece of information. In fact, the USDA carried out a study which concluded that the calories our body “absorbs” from nuts are on average 32% less than the calorie count listed on food packaging.

Furthermore, this conclusion was made relating to the “average person”. But what does “average person” mean? It’s challenging to make such a generalisation because as we can imagine, people differ widely from one another, and so many factors, from age to gender to bodyweight can influence our daily energy requirements as well as energy expenditure. 

Indeed, the USDA study found that the number of calories absorbed from an ounce of almonds varied hugely between individuals, from as low as 56kcal per ounce to as high as 168kcal per ounce!

This goes to show that the exact same number of almonds can translate to very different calorie counts depending on the individual.

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