Calculation, concept … How do calories work?

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Calculation, concept … How do calories work?


There is a lot of talk about calories in the world of nutrition. But concretely, what do calories represent? How Much Should You Eat in Your Diet Each Day? Is it that important? We take stock of all these questions in the company of Anne Colin, dietitian nutritionist.

Understanding what calories are for the body

Before talking about diet, it is important to talk about physics, to understand what calories are in concrete. This is an international unit of measurement, originally used to calculate the energy needed to heat one gram of water from 14.5 to 15.5 degrees. Finally, this unit of measurement was gradually abandoned by physicists, but is still used in the world of nutrition and dietetics. The calorie is therefore used today to calculate the energy value of a food. The most common measure is the kilocalorie (Kcal) which corresponds to 1,000 calories.

What a daily calorie requirement: do not forget the nutrients for the body!

Calories can be converted depending on the nutrients present in the food. So, for 1 gram of lipids, we get 9 Kcal. For one gram of carbohydrates we get 4 Kcal, for 1 gram of protein we also get 4 Kcal and, finally, 1 gram of alcohol provides 7 Kcal. To get the caloric value of a food, we then calculate the total amount of nutrients present.

But be careful, because as Anne Colin summarizes, calories are an indicative element: “There are many calories in a glass of beer, but that does not mean that you only need to drink beer to consume them daily. Calories. That would be too simple. It is also necessary to take into account. of the nutritional elements present in food. Iron or zinc, for example, are very important for the development of the organism but have a very low calorific value. You need to be able to juggle these different parameters to have a good diet “.

How are calories consumed?

The consumption of calories is multiple within our metabolism! If sports activity can be gluttonous of calories, it is the entire human body that has a significant caloric requirement. Daily movements and any physical activity, whatever it may be, can therefore need energy! Namely: brain activity, heartbeat, digestion, cell renewal or breathing all consume energy in the body. It is therefore necessary to be wary of too restrictive diets, because vital functions could be slowed down with a caloric intake lower than that necessary for good health.

How many calories a day: what is the recommended daily calorie intake for men and women (in Kcal)?

There is an average of recommended kilocalories for adults. Although mainly indicative, this allows you to have an idea of ​​the amount of calories to be ingested each day. Average calorie intake varies between men and women, so for men the calorie requirement is between 2400 and 2600 kilocalories per day. For women, the average daily calorie requirement is slightly lower and it is between 1800 and 2200 Kcal per day.

As for the nutrients present in our diet, it is recommended to consume 55% of carbohydrates per day. It is also recommended to consume 30% fat and 15% protein.

While the average daily calorie requirement can give an indication of what we should eat each day, it remains inaccurate. Each person, man or woman, in fact, has a different metabolism, but also a specific physical activity that will generate a very different caloric requirement depending on the individual. There is a method that allows you to more accurately calculate your daily calorie requirement. This is Harris and Benedict’s formula:

Harris and Benedict’s formula:

The daily energy requirement (BEJ) is calculated by multiplying the basal resting metabolic rate by the activity level.

For metabolism, proceed as follows:

For men, we multiply his weight (in kilos) by 10, which we add with his height (in cm) multiplied by 6.25, which we then subtract by his age in years multiplied by 5. We add 5 to the result.

So, for a 25-year-old man who measures 1.72 meters tall and weighs 65 pounds, we’ll get (65 * 10) + (172 * 6.25) – (25 * 5) +5, which gives us 1855.

For women’s basal metabolic rate, it’s the same calculation with the difference that we remove 161 instead of adding 5 to the end of the calculation.

Once you have your basal metabolic rate, you need to multiply it by the physical activity coefficient:

  • The latter is 1.2 if sports spending is low (sedentary lifestyle)
  • 1.375 if the sporting activity takes place from 1 to 3 times a week
  • 1.55 if physical activity takes place between 4 and 6 times a week
  • Finally, the coefficient is 1.75 if the sport activity is daily

For example, if the metabolism calculated above is linked to zero sports activity, the daily caloric requirement will be 1855 X 1.2, or 2226 Kcal.

With this calculation you will get more precisely the daily energy requirement of your body.

The daily energy requirement in children

Unlike adults, children have an additional parameter that increases their daily calorie needs: growth. In fact, with the passing of the years, the energy needs increase in the little ones. Obviously, every child has a different body and a specific need. On average, children between 3 and 9 years of age are advised to consume between 1200 and 2000 Kcal per day. Between the ages of 10 and 18, the energy requirement will be between 1900 and 3000 kilocalories per day.

How many calories do pregnant women need?

When you are pregnant, you shouldn’t “eat for two”, it’s common knowledge. But we must also eat twice as much! During pregnancy, calorie needs only increase slightly over the months. The European Food Safety Authority advises pregnant women to make these additions to the calculation of the daily energy requirement shown above:

– We add 70 calories every day in the first quarter

– We add 260 calories every day in the second quarter

– We add 500 calories every day in the third quarter

Finally, if we breastfeed, we also add 500 kilocalories per day, because the production of breast milk also consumes energy.

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