HOW TO CALCULATE FOOD CALORIES?
On a regular shopping visit at a grocery store you will always see the same picture – people talking about calories, people calculating calories, people limiting calories. All the boxes and packages are having a lengthy explanation of the nutrition facts and calories of the product. We all read them carefully and yet, do we know what do they mean?
The simplest way to understand the calories is to think about them as energy. And as energy we will be surprised to find out what a certain amount of food can do. For example a 60W light bulb can be kept lighting for an hour and a half by the calories hidden in just a simple slice of a beautiful cheese cake. And the calories in approximately 220 Big Macs will keep a car driving for more than 80 miles. So how much calories do we, as humans need to keep our life lighting and smoothly running?
Despite the common perception of the calories we have, being associated with food, a calorie is just a unit of energy. By definition,
one calorie represents the amount of energy needed to raise by one degree Celsius (1.8 degrees Fahrenheit) the temperature of one gram of water.
In physics, one calorie equals to 4.184 joules. The so called food calories, which we read on the food packages are actually written in kilocalories (1000 calories = 1 kilocalorie). That is one food calorie being equal to 4 184 joules. Lets use a can of soda for example. It contains approximately 200 food calories, which is
200 food calories = 200 000 regular calories = 200 kilocalories = 836 800 joules
And here’s something interesting to simplify the math, 1 gallon of gasoline contains 31 000 kilocalories and one mile of jogging makes us lose about 100 kilocalories! Not bad for the runners!
So how much energy do we really need for a healthy living? The calories we get from the food are built up from three main components – carbohydrates, protein and fat.
1 gram carbohydrates = 4 food calories (4 000 regular calories)
1 gram protein = 4 food calories (4 000 regular calories)
1 gram fat = 9 food calories (9 000 regular calories)
So if we know how many grams of carbohydrates, protein and fat a particular food contains, we will be able to calculate how many calories, respectively how much energy that food contains.
Let’s analyze the nutrition table at the back of a Multigrain Snack Crackers container.
11 g carbohydrates = 11 x 4 = 44 food calories = 44 000 regular calories
1 g protein = 4 food calories = 4 000 regular calories
2.5 g fat = 2.5 x 9 = 22.5 food calories = 22 500 regular calories
Now let’s add the food calories
44 + 4 + 22.5 = 70.5 food calories = 70 500 regular calories,
which is an underestimation of the listed in the table total amount of 70 calories. If we do similar calculations for other products, we’ll see that in most of the cases manufacturers prefer to underestimate the total amount of calories. Apparently this is a regular practice. So if we eat 10 crackers from the Multigrain box we will be in possession of an energy enough to raise by one degree Celsius the temperature of 70.5 kilograms of water!
Of course, not all of this energy is put into use the way we understand it. Through a process called cellular metabolism our body “burns” the energy components protein, carbohydrates and fats into amino acids, glucose and simple sugars, and fatty acids and glycerol respectively, giving as waste products NH3, HO2, and CO2
So how much energy, or how many calories our body needs to function properly and keep healthy?
let’s have a cracker and stay tuned for our next article.