Calories - What exactly are they? June 20, 2012
Calories - What exactly are they? June 20, 2012

Calories; they are everywhere these days. We count them, consume them, and cut them. Whenever anyone mentions food or exercise, the main topic is always about how many calories did you eat or burn. But if asked, I doubt few people would actually know what a calorie really is. Most would probably say something like “aren’t they an ingredient in food that makes me fat?”

A calorie is basically a unit of energy, or more accurately, a unit of heat. It was first defined by French physicist Nicolas Clément in about 1824. It was originally used as a way to measure heat which has since been replaced by the joule. It is now commonly used as a unit of food energy. This is where the term “burning calories” come from.

There are actually two classes of calorie; a small calorie (cal) which is the energy needed to increase 1g of water by 1ºC, and a large calorie or food calorie (kcal), which is the energy needed to increase 1kg of water by 1ºC.

Although most often times associated with food, calorie measurements can be applied to anything that contains energy. For example a gallon of gasoline contains about 31,000,000 calories.

We get our energy from consuming all different types of food and break it all down during digestion to release the energy. The number of calories in a specific type of food relates to the amount of energy that can be acquired from it. In general, 1g of fat contains 9 kcals and a 1g of carbohydrate or protein contains about 4 kcals of energy each.

We all require a certain amount of energy to survive. There are hundreds of processes going on inside our bodies all day, every day, most of which we don’t even know about that all require energy. Our brain, heart, lungs, muscular and nervous systems are constantly functioning, even while we sleep or lie on the couch watching TV. All of this requires energy, which we calculate in calories.

We also have something called our Resting Metabolic Rate (RMR), which is the minimum number of calories needed to survive. This varies greatly depending on age, gender, weight and muscle mass. This RMR does not take into account any activity of daily living or exercise. The average adult has a RMR of between 1000-1400 calories just to survive.

If you increase your food intake and hence your caloric intake past a point of what you require for your RMR, these extra calories are stored as a couple of different forms of energy in a few places in the body. One form is glycogen which is stored mostly in the liver and is an immediate source of energy that can be quickly and easily tapped into. Another form of this extra energy is fat, which is stored in many fat sites around the body. Fat stores are a little harder to tap into and take longer to convert to energy than glycogen, but are ultimately a richer source of energy.

This brings us to the all-important Caloric Balance, which is a very basic equation of calories in versus calories out. To be in perfect or equal caloric balance, you need to burn the same amount of calories that you consume per day. If you are in a positive caloric balance then the extra calories you consume are stored and you gain weight. If you are in a negative caloric balance then you are burning more calories than you are consuming and will lose weight. Simple, right?

There is another factor than can play a major role in caloric balance; exercise. Remember your RMR does not include your activity or exercise. So increasing your activity or exercise levels will increase your daily energy requirements and can have a big effect on your caloric balance and your RMR.

To really affect a negative caloric balance, a combination of both reduced caloric intake and increased daily activity or exercise is the best option. Therefore, diet or exercise alone will unfortunately not cut it –you really need a good combination or balance of both.

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