Everything you ever wanted to know about calories (but were afraid to ask)

When it comes to training, weight loss and healthy eating, one word is mentioned with striking regularity: calories. Here is a collection of all the questions and answers about calories.

Calories is a word which has now entered the social consciousness and is one that everybody knows. Some more in-depth followers will also have a bank of knowledge detailing how many of these calories their foods contain.

Despite this, the calorie is also one of the most misunderstood measurements in common usage. Few are aware of exactly what a calorie actually is or what effects they have on the body (other than the cripplingly vague and not quite true "make you fat").

So for this reason, here is a beginner's guide to the calorie, acting as a way of getting to know this oft-regarded but similarly misunderstood measurement.

What actually are they?

First, it's worth discerning between the two types of calorie. In a scientific sense, a calorie is an SI (Système International d’Unités) unit of energy, although these days it has been largely usurped by the now-commonplace joule.
The scientific calorie is an indicator of how much heat would be needed to raise one gram of water by one degree Celsius.

Food calories, on the other hand, are - strictly speaking - kilocalories, measuring 1,000 times their scientific namesakes. For the remainder of this article, however, they will be referred to as the widely-accepted 'calorie'. 

These calories are a measurement of how much energy a food contains. The higher the volume of energy it provides, the more calories it contains.

This relationship between scientific and food calories does throw up some interesting statistics, however, as they both deal with energy.
For example, a typical fast food burger will contain over 500 calories, meaning it could power a 100 Watt light bulb for more than six hours.
Even a typical large coffee from the high street retailers could power an LCD TV for eight and a half minutes.

Working out calorie counts

Finding out how many calories a food item contains is relatively easy.
A gram of carbohydrates, for example, contains around four calories, as does a gram of protein.

Fat, on the other hand, contains roughly nine calories per gram, which is why sweet treats containing butter deliver significantly more on the calorie count.
The difficult part is knowing how many of these so-called 'building blocks' of food each item contains. With that worked out, however, the calorie count is sure to follow.

'Burning' calories

When exercising, one of the most popular reasons is to 'burn' calories.
This simply involves upping the body's need for energy in order to process what's been eaten and ensure no food energy is left over at the end.
Any calories left over after the exercise has 'burned' them and the body has taken all it needs in order to actually function will then go toward building muscle or storing fat, depending on the exercise level and type of workout.

For this reason, those who want to lose weight will need to exercise enough to burn more calories than they take in.
This can be measured by simply working out (via a food diary or similar) how many calories they eat then ensuring a few hundred more are burned.
This is effectively achieved using aerobic exercises, such as running or rowing. 
It's important, however, to also consider the calories the body would need to function, so going too far in any direction is not advised.

Those looking to build muscle, however, may wish to utilize a 'calorie surplus'.
This would involve taking on more calories than are being burned off, and undertaking plenty of anaerobic exercises.
The exercise will build muscle, while the extra calories can supplement this during rest periods.

How many do we need?

Calorie counting is, for many people, more of an art than a science as it can vary wildly from person to person.
While some may have fast metabolisms, others may not.
This isn't just true of different individuals, but can change for an individual over the course of their lifetime.
There is also the issue of how much exercise a person gets to do, the intensity of their job and the simple variable of whether they are male or female.

The rule of thumb is that average, healthy men should take on roughly 2,500 calories per day, while the figure for the average woman is closer to 2,000.
Those wanting a more specific answer, however, can look at their Basal Metabolic Rate (BMR), which takes into account weight, height and age to provide the exact number of calories an individual would need for the body to function at rest.
Roughly, this represents around two thirds of the total number of calories needed per day, with the remainder then going towards physical activities, such as walking to work or running for the bus.

There are a number of different ways to work out a BMR, with some dating back almost 100 years.
One of the most trusted is the Harris Benedict model which for adult men is:

66 + (6.3 x body weight [lbs]) + (12.9 x height [inches]) - (6.8 x age)

Women use a similar setup but with amended figures:

655 + (4.3 x weight [lbs]) + (4.7 x height [inches]) - (4.7 x age)

The result should give an accurate idea of the minimum number of calories each person's body would need to function fully at rest.

Knowing this information about calories probably won't make the gym any easier.
It certainly won't help continue for the last minute on the treadmill when your legs are screaming, that's for sure.
What it should do, however, is provide the  knowledge needed to create a tailored plan that will work better than an off-the-peg alternative.
It gives those undertaking exercise an idea of what to achieve, but also how to keep their body at a safe level, ensuring that the hard work pays off.