Calories for beginners

Let's start from the beginning.. I'm going right back to basics so if you're already an experienced calorie counter like me, please bear with me. If you're new to the world of calories and macronutrients, then you're in the right place!

What are calories?

Calories are smaller version of Kilocalories; 1 Kilocalorie = 1000 calories.

Kilocalories (Kcal) are a unit of measurement for energy which can be converted into kilojoules, the same way that centimetres can be converted to inches. 1 Kcal equals 4.18 kilojoules.

A calorie refers to the amount of heat needed to raise the temperature of 1 gram of water from 14.5 to 15.5 degrees celcius

A Kcal in nutrition is 1,000 of these small calories.

1 Kilocalorie = 1000 calories = 4.18 Kilojoule

Nutritional Kilocalories are usually referred to as calories for simplicity sake and from here forward will be referred to as such.

Calories or kilojoules can be stored in many different ways; coal, gas and wood are all stored energy. Firewood for example is a form of energy which is stored as carbon. Trees take energy from the sun, air and earth and store that energy as wood (carbon); this is how trees grow. When you burn the firewood, energy (kilojoules) are released as heat (fire).

If you can set it on fire, it has stored energy.

The same concept applies to your body in a nutritional sense. Energy is stored in the form of calories in food. The only difference is that our body doesn't set things on fire to release the energy, it digests it.

If most forms of matter contain energy then why can't we eat wood?

Well, aside from the fact that it would be pretty difficult to chew, we lack the stomach enzymes to actually convert this kind of matter into useable energy. So if we ate wood or coal, we would just poop it out, undigested. Different animals however have different stomach enzymes and can turn tree bark, grass, and other forms of matter into useable energy.

When you digest food, the energy needs to go somewhere; basic physics dictates that energy cannot just vanish, it MUST be converted. The energy from food enters your blood stream as glucose. Any glucose that is not used gets converted to glycogen and stored in the liver; here the glycogen can be easily converted back to glucose and used as energy if required. If unused, this glycogen will turn into fat and store on the body for long term use.

This is called a calorie surplus.

The opposite applies for a calorie deficit. If you use all of the excess readily available glucose and glycogen, your body will turn fat into glycogen and glycogen into glucose for energy. This is called a calorie deficit.

This energy is released, in the same way as fire wood, through heat. Your body heat is a result of calories being "burnt".

Ever wondered "where does my fat go when I lose weight?"

Similarly, have you ever wondered "Where does wood go when you burn it?"

Both are released as heat.

It is easy to see then, why weight gain and weight loss comes down to the simple maths of energy in vs energy out.

Next week I will discuss macronutrients; carbohydrates, protein, fat. Please subscribe if you would like to be notified when the next blog is ready to read!

Yours truly,

The Fit Nurse

Tuscany vineyards: A picture taken soon after consuming many calories in the form of wine ;)