Calories explained. Where do the numbers come from?

One would naively think that when someone or some company starts to develop and sell a new food product or a chef invents or reinvents some recipe, they actually invest in a lab test that would count the calories based on some complex unknown maths. Well, while there are lab tests behind it, most of the popular foods have had tests done decades ago and industry today still takes advantage of them, without even contributing to the costs of those tests.

How do we calculate the number of calories?

So you might already know this, if you don’t here it is. Foods are made up of 3 major nutrients: carbs (short for carbohydrates), lipids, also called fats, and proteins. Minor nutrients include minerals (like salt and calcium), antioxidants (like vitamin C) and water, but these don’t have a major influence in the energy related processes of our body – we don’t count them.

You might be surprised that all the calories are based on just the quantity of the three major nutrients in foods (also called macronutrients).

1 gram of carbohydrate¬†gives our body 4 calories, same as 1 gram of protein, while 1 gram of fat gives 9 calories. One particular substance is important in calorie numbers, and that’s alcohol, which counts 7 calories per gram, which is almost double the amount for sugar. Not mentioning the amount of toxins that alcoholic drinks also contain.

How do we know this?

These numbers are based on some lab tests done decades ago, when someone actually counted the number of nutrients per a specific product quantity. So, for example, they got to the conclusion that the chicken meat has approximately 24 grams of protein per 100 grams of product. And the list goes on with meats, cheeses, cereals, legumes, vegetables, fruits, etc. Back to nowadays, when someone produces a food, it just adds up the number of grams for each major nutrient in the ingredients used, multiply that number by the number of calories per gram and ta-daaa, that’s the weird number you see on the pack, even though it seems random. All numbers are on Wikipedia. You can just fire up your search engine and query for these numbers and there you go, you got the number of calories from the comfort of your home. Or your factory.

How many calories do we need?

Regarding the number of calories each person should consume daily (DCN – Daily Caloric Need), this depends on many factors and one’s own exact number can only be found by doing specific tests. But it can also be estimated using some very simple formulas, explained as follows.

It all starts with the BMR – Basal Metabolic Rate – which is the energy (in calories) that the body spends at rest, so considering only base body functions (blood circulation and heart beating, lungs breathing, maintaining body temperature, etc). Usually, the BMR represents 60 to 75% of the calories we burn daily. Generally, men have a higher BMR than women.
A rule to compute the BMR is multiplying your weight in kg with a factor of 22 for women and 24 for men. So a 50kg woman would have an approximate BMR of 50 x 22 = 1100 calories. Similarly, a 70kg man would have a BMR of 70 x 24 = 1680 calories.

A second factor comes into place when calculating DCN, and that is called PAL – Physical Activity Level:

  • 1.2 for people that are mostly inactive or sedentary
  • 1.3 for people fairly active, for example that walk a lot and exercise 1-2 times a week
  • 1.4 for people moderately active, 2-3 times a week
  • 1.5 for active people exercising more than 3 times a week
  • 1.7 for very active people that do intense exercises daily

To calculate DCN just multiply BMR with PAL. So, a sedentary 70kg man has a daily cap in terms of the number of calories to consume and maintain weight of: 1680 x 1.2 = 2016 calories. An active 50 kg woman exercising 2-3 times a week needs a daily 1100 x 1.4 = 1540 calories.

How can I gain or lose weight?

Approximately half of a kilogram (one pound) of body weight counts for 3500 calories. Eating more than the DCN would cause gaining weight, similarly, to lose weight, you just need to cut the DCN with a number of calories. For example, cutting 100 calories from your daily intake would mean that, without any additional lifestyle change, you would lose a pound over 35 days.


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