What Is A Calories? How Do Calories Work?

What Is A Calorie? A Calorie … the number we..

What Is A Calories? How Do Calories Work?

What Is A Calorie?

A Calorie … the number we assign to food that tells us how much we’re supposed to eat in a day, right?

Well, at least that’s how our dieting culture has defined a Calorie.

But in reality, it is a bit trickier to quantify than that. You can have a small handful of food be more Calories than a large plate full of food, and the other way around.

So if a Calorie doesn’t reliably define a set amount of food. Yet is largely understood to dictate the amounts we should be eating.

What exactly is a Calorie?

A Calorie (or more precisely – a kilocalorie) is a unit of heat.

We associate a unit of heat energy to our foods because it approximates the capacity within the human body to create heat via metabolism (i.e., the breakdown of food into energy).

The mathematical formula used to define 1 Calorie is that 1 Calorie is the heat energy required to raise 1 Liter of water by 1 degree Celsius.

In order to determine how much Caloric energy food contains, scientists use a device known as a bomb calorimeter.

This device works by placing a set weight of food (for instance, 1 gram of fat) into a container that is surrounded by a set volume of water (for instance, 1 Liter of water).

And then setting the food on fire to see how much of an influence the heat has on the surrounding water.

Scientists have measured the caloric values of different types of food with bomb calorimeters.

Which we see represented on our food labels as the Calories associated with fat, carbohydrates and protein.

  • 1 gram of fat would increase 1 Liter of water by approximately 9 degrees Celsius, thus 1 gram of fat has 9 Calories.
  • 1 gram of carbohydrate in a bomb calorimeter raises 1 Liter of water by about 4 degrees Celsius so we say that 1 gram of carbohydrate has 4 Calories.
  • Protein is a bit trickier in a bomb calorimeter, because about 20% of protein (by weight) is nitrogen, which cannot be used by the human body for energy production. After accounting for nitrogen, it is determined that 1 gram of protein raises 1 Liter of water by about 4 degrees; thus we associate 1 gram of protein has 4 Calories.


The human relationship to food ranges from what is culturally defining to the memorable and tastes from childhood.

But the most important reason behind eating food is its biological purpose to fuel everything happening inside our bodies.

If you cut back on your Calories too much. Then you are essentially cutting back on your body’s ability to produce energy via metabolism.

If you consume too many Calories, then, in your body’s efficient wisdom. You will store what you don’t immediately use for energy production into the ultimate-fuel-storage-depot – adipose, or body fat.

The goal for optimal health is to aim for nutrient-dense foods to provide adequate Calories, paired with healthy physical activity.

The physical activity serves as the metabolic drive to use the foods you eat for energy production. Keeping your body strong, well fueled, and satisfied.

Calories in, Calories out

There are two ways in which you might want to track calories:

  • How many you consume – how much energy you take in.
  • How many calories you burn during exercise – how much energy you put out.


If you eat more calories than you need (for normal metabolic functions and for the activity which you do), then your body will store the extra energy as fat.

If you eat fewer calories than you need, your body will burn fat to provide the extra energy.

How many Calories should I be eating?

Generally, the recommended daily calorie intake is 2,000 calories per day for women and 2,500 for men.

However, the government is currently reviewing this – suspecting that our sedentary lifestyles mean that fewer calories are needed in order to maintain a healthy weight.

If you’re trying to lose weight, most nutritionists recommend a calorie range between 1,200 and 1,800 for optimum weight-loss.

The more overweight you are to start with. The more calories you can eat – as heavier bodies need more energy just to function.

You shouldn’t drop below 1,100 calories, and certainly not for an extended period of time.

Daniel Messer, RNutr, CPT

We eat clean, are always motivated and helpout beginners in need. We sell guides on Cutting, Bulking and Muscle Building. Checkout our website!

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