How to determine your daily calorie needs

As I was searching for literature for this introductory chapter in nutrition, I came across this question: »You've probably heard about calories. Are they good or bad for you?« Now this question had me confused and, quite frankly, dumb founded for a while. Aren't calories already common knowledge? We see them every day and they are clearly written on 95% of the food labels, surely people know what they are.

Immediately I called up a few of my friends and asked them, if they could give me a brief explanation about what a calorie is. To my surprise, none of them could give me a good explanation, even though one is a medical student, 2 are personal trainers and one is a dietitian. All of them are people, who should know almost everything about proper nutrition, especially the dietitian.

What does a car need to run? Fuel, of course. How about our bodies? Our bodies need a fuel source as well, and that fuel comes in a form of food. If you want to know what is a healthy and effective way to lose fat or to bulk up with muscle, you need to know at least the basic on calories.

Weather your goal is to lose or to gain weight, you must keep in mind one thing. Weight loss or weight gain is nothing less than. simple math. Simple addition and subtraction is all you need. But I’m getting a bit ahead of myself. Let me explain what calories are.

Let me make something really clear. Calories (kcal) are nothing more than units of energy and for this part, I’ll just focus on the calories in food. Carbohydrates, proteins and fats have a caloric value, most of us know that. 1 gram of fat has 9 calories, 1 gram of carbohydrates 4, and 1 gram of protein 4 calories. But our food is not just made up from those 3 macronutrients.

Organic acids, polyols, water soluble fiber and ethanol also have calories. 1 gram of ethanol has 7 calories, putting it in the second place, right behind fats, while the other three have less than 4 calories per gram.

[There is a big difference between calories and Calories, but unless you are a physicist, you don’t need to worry much about those. The first one means 1000 calories, because some countries like US and Canada want to make sure, that the food labels are as easy to understand as possible. In the broader context it really doesn’t matter that much how they are written, as long as you know how much energy you are putting in your body.]

Firtst thing that you need to do is to determine, how much energy your body needs during the day. This can be easily done with a simple basal metabolic rate calculation. Basal metabolic rate (BMR) tells us the amount of energy our bodies need just to survive during the course of one day. This can be done with the following formulas:

Men: BMR = 66 + (13.7 x weight in kg ) + ( 5 x height in cm ) – (6.8 x age in years )

Women: BMR = 665 + (9.6 x weight in kg ) + ( 1.8 x height in cm ) – ( 4.7 x age in years )

Or you can just search for one online, just be sure to type basal metabolic rate formula or BMR formula.

For example, let’s take a 30 year old woman, who is 156cm tall and weighs 70kg

BMR = 665 + (9.6 x 70 ) + ( 1.8 x 156 ) – ( 4.7 x 30 )

BMR = 665 + 672 +280.8 –141

BMR = 1476.8 kcal

So this woman needs to eat around 1480 kcal every day, just to function normally. This is a number that tells us, how much energy her body will burn by itself just by existing.

But as we all know, there is more to life than just existing. We have jobs, kids, friends, we go out, exercise, clean… our lives are not just stuck in one place. And by doing the things that we do, we need more energy (because every move that we make requires a certain amount of energy).

This is why we need to know our active metabolic rate (AMR). AMR is the amount of energy we need to function through the day. It includes everything from our internal metabolism (nails and hair growing, keeping our bodies warm, transportation of different substances in and out of the cells) to our daily actions.

I prefer to use the Harris Benedict equation which states:

1.       If you are sedentary (little or no exercise) : = BMR x 1.2

2.       If you are lightly active (light exercise/sports 1-3 days/week) : = BMR x 1.375

3.       If you are moderatetely active (moderate exercise/sports 3-5 days/week) : = BMR x 1.55

4.       If you are very active (hard exercise/sports 6-7 days a week) : = BMR x 1.725

5.       If you are extra active (very hard exercise/sports & physical job or 2x training) : = BMR x 1.9

Let’s go back to the woman in the previous example and say, that she is a teacher and doesn’t move around a lot during the day. So we just take her BMR and multiply that by 1.2

AMR = 1476.8 x 1.2

AMR = 1772.16 kcal

This woman must eat around 1780kcal to be able to function normally through the day and to keep her current body weight.

But this woman wants to lose weight, so what do we do now?

Well, 1kg of body fat (notice how I said body fat and not body weight) has 7700 calories stored in it, and I’ll tell you more on that next week.

Until next time, stay strong and be kind.

Picture taken from http://tiny.cc/wgvmhw