Calories. We’ve all heard of them. Especially over recent weeks where the news is full of articles about laws enforcing restaurants to detail calories on their menus. But do you really know what calories are? Are they something to be afraid of? Do you know what to look out for?

What are Calories?

In short, a calorie is a unit of energy and can be used as a measurement for anything that produces energy – whether that be nutritional energy (food) or other types of fuel (e.g. coal).

Why do we need Calories?

The human body requires energy (calories) to survive, even at rest. Calories are used by the body in many ways and some you may not even be aware of. The most obvious use of calories are physical activity and growth. But did you know that the majority of calories consumed are actually used by your body elsewhere?

Basal metabolism (c. 65-75% of the calories you consume) – this involves all activities that are essential for life. This includes functions such as:

  • cell function and replacement
  • maintenance of body temperature
  • un-interruption of cardiac and respiratory muscles
  • brain function

Thermal Effect of Food (c. 10% of the calories you consume) -  this involves the body’s functions to digest and absorb nutrients.

How many Calories do I need?

According to the NHS, as a guide, an average man needs to consume around 2,500kcal a day to maintain a healthy body weight. For an average woman, that figure is around 2,000kcal (8,400kJ) a day. (These values can vary depending on age, size and levels of physical activity, among other factors).

Maintaining a healthy body weight means that you are burning (using) all the calories consumed to fuel the body.

If too many calories are consumed, the body will store this energy to use later in the form of fat which in turn causes weight gain. In this instance, the number of calories consumed needs to be reduced (calorie deficit). A calories surplus of c.3,500 calories will cause a weight gain of 1lb over any given period of time. For example, over a 2-week period, this would be 250 calories per day.

If not enough calories are consumed, the body will use fat as an alternative energy source which results in weight loss. In this instance, the number of calories should be increased.

How do I track Calories?

Despite what we read on social media or the news, calories are not bad. All foods are measured in calories, given that they provide energy (whether it be a piece of chocolate cake or an apple). It is just that some food contains more calories than others.

As a general rule, fats contain the highest in calories:

Carbohydrates = 4kcals per 1g

Protein = 4kcals per 1g

Fat = 9kcals per 1g

It is also important to remember that portion size also impacts the number of calories. For example, almonds are a healthy snack given that they are highly nutritious and rich in healthy fats, antioxidants, vitamins and minerals. However, a portion of 15 almonds contains the same number of calories as a 2-finger KitKat contains.

Some people chose to track their calories each day to ensure that they stay on track depending on their personal goal (e.g. lose weight). This can simply involve reviewing food label but can also involve weighing food (depending on the person’s preference). This is a proven way to stay on top of calories, however this is not for everyone and should not be avoided by those who have a disordered relationship with food. The other option is to be mindful when picking food. Reviewing labels on food can give you the information you need in regards to calories and help you make an informed decision on what is best.


Remember, all food contains calories! Enjoy them… wisely!

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