Nutrition

What Are Calories?

What Are Calories?

We hear about calories pretty much everyday, but do you really understand what they are? If not then you’re about to find out.


What Are Calories?

A calorie is a unit of energy. It is the approximate amount of energy needed to raise the temperature of one gram of water by one degree Celsius at a pressure of one atmosphere. In a nutritional context, the kilojoule (kJ) is the unit of food energy, although the kilocalorie is still in common use. The word calorie is popularly used with the number of kilocalories of nutritional energy measured. As if to avoid confusion, it is sometimes written Calorie (with a capital “C”) in an attempt to make the distinction, although this is not widely understood. This is why you will see kCal written on food labels.

To facilitate comparison, specific energy or energy density figures are often quoted as “calories per serving” or “kilocalories per 100 g”. A nutritional requirement or consumption is often expressed in calories per day. One gram of fat in food contains nine kilocalories, while a gram of either a carbohydrate or a protein contains approximately four kilocalories. Alcohol in a food contains seven kilocalories per gram.

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How Do You Burn Calories?

Metabolism is the process by which your body converts what you eat and drink into energy. During this complex biochemical process, calories in food and beverages are combined with oxygen to release the energy your body needs to function.

Even when your body is at rest, it needs energy for all its hidden functions, such as breathing, circulating blood, adjusting hormone levels, and of course growing and repairing cells.

The number of calories your body uses to carry out these basic functions is known as your basal metabolic rate — what you might call metabolism. Several factors determine your individual basal metabolic rate, including, age, sex and your body size and composition.

The energy your body requires for basic functions stays fairly consistent and is not easily changed. Your basal metabolic rate accounts for about 70% of the calories you burn every day. In addition to your basal metabolic rate there are two other factors which determine how many calories you burn each day, your processing of food and your physical activity level.

Food processing includes digesting, absorbing, transporting and storing the food you consume. This can range from 100 to 800 of the calories used each day and again this stays fairly consistent. Physical activity accounts for the rest of your calorie burn and is the most easily varied factor that affects your daily caloric output.

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Factors affecting your Basal Metabolic Rate (BMR)

✓ Genetics

Interestingly genetics affect your BMR, way back in time when we had to hunt for every calorie we consumed many evolved to be efficient human beings and slow down their calorie burn at rest in order to save energy for when they needed it, so now some people have that gene in them and have a slower resting metabolism.

✓ Muscle Mass

Muscle tissue is the most metabolically active in your body and so by gaining more of it you increase your BMR, so the breakdown of old protein and synthesis of new protein accounts for around one fifth of your BMR. So gaining more muscle will cause you to burn more calories even while you rest.

✓ Amount You Eat and What You Eat

This is why many diets fail, another evolutionary trait, when you severely restrict your calorie consumption your body goes into survival mode and tries to hold onto as much energy as possible. This is why you need to make sure you consume enough calories each day and only eat at around a 500 calorie deficit when attempting to lose weight.

Also protein is the macronutrient that is hardest to break down and therefore takes more calories to do it, by eating high protein meals your body will burn more through digesting it. The same goes for fibrous carbohydrates as they are harder to break down than refined carbs.

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Take Home Message

As great as it is to try and increase your basal metabolic rate the difference you need can be made by pushing your physical activity up a notch. Many people do not realize how small a change needs to be made in order to efficiently lose weight. All it takes is some patience and good old fashioned hard work. Eat clean foods, exercise thoroughly and track what calories you take in. Now that you understand what a calorie is and what you need to do to make effective use of them and burn them, you should be ready to make the changes you need to see results in the New Year. Good luck!

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Kevin Dickson

Kevin Dickson

Writer and expert


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