First to clarify, calories are broken into small calories and large calories. A small calories is 4.2 joules and one large calories is 4.2 kilojoules.
When we talk about one calorie in nutrition we speak of the large calorie. The word kilocalorie just means 1 000 small calories.
In order to calculate calorie intake we need to break down the type of intake and the amount of intake.
Food intake can be broken down into three things:
Next we need to find out how much of this is in the food you eat. For example, a person might have eggs, bacon and toast for breakfast. In that one breakfast alone there will be a certain amount of carbs, fats and proteins.
Each of these has their own calorie content which is as follows:
The next step is to find out how much protein, carbs and fats are in your breakfast. Usually youâ€™ll find the numbers on the packaging but weâ€™ll just do this hypothetically.
Usually the packaging will list the carb, fat and protein amounts per 100 grams and per serving.
Suppose the protein content is 20 grams per every 100 grams of meat and there is 200 grams of meat on your plate. This means there is a total of 40 grams of protein. (Meat will also contain fat etc. so you simply calculate the fat amount in the same way for the meat)
With the same method we can tell the carbohydrate amount. If there is 50 grams of carbohydrates per 100 of bread and you have 50 grams of toast on your place, then this means there is 25 grams of carbohydrates.
Suppose you do the same calculation with the fat content and come up with 20 grams of fat.
We are left with something like this:
All you have to do now is multiply the amount with their calorie value.
When we combine both the calorie amounts we are left with a total amount of 440 calories.
Itâ€™s important to remember that this is just a system and guideline for calorie intake. The body burns fat, protein and carbohydrates at different rates and also uses protein as a last resort for fuel.
This means that when you burn calories during training, your body will burn certain portions first depending on your intensity levels.