Calories vs. Kilojoules: Why the Kilojoule is an Ineffective Measure if You Want to Stay Thin

Metric and imperial – will the war ever end? As a child, I spent two years in the American school system, learning about inches, quarts, pounds and dimes. Then it was back to the Australian school system for me where I learnt about centimetres, millilitres, kilograms and ten cent pieces. To make things even more confusing, I was transferring in grade school, when many of these important measures are first learned and committed to memory.

Bar far, the metric system is superior for measuring.

No, no… don’t get mad – we all know it’s true. It makes a lot more sense, for a start. It’s quite funny because things only started to get metric here in Australia in the 60s, meaning that half the population is still very confused daily.

Technically, the calorie and the kilojoules are BOTH part of the metric system. The calorie was first defined by Nicolas Clément in 1824 as a unit of heat, deriving from the Latin word calor meaning “heat”.

Sadly – and much to my horror and chagrin, calories have “now been superseded in the International System of Units by the joule” according to wikipedia. The site does go on to mention “in spite of its non-official status, the large calorie is still widely used as a unit of food energy in the US, UK and some other Western countries.”

And this is where my rant comes in (you knew you were about to get one of my rants, didn’t you?).

For my money, the calorie is by far the more efficient method of measuring the energy vales of food. Why? Because it’s a smaller unit. For this reason, I am also in favour of the kilogram versus the pound, but that’s a whole other story – we don’t need to count those hourly and daily, do we?

It’s easy for me to understand that I should be eating 300 to 400 calories for lunch, but my brain fades when the figure turns to 1260 and 1680. My mind automatically tends to round those figures up, saying, “well, ok, that’s approximately 2000 kilojoules”. Every day I can eat 7560 – so if my burger is 1570 then how much is left?

Kilojoules will drive you insane.

“One calorie is approximately 4.2 joules. The factors used to convert calories to joules are numerically equivalent to expressions of the specific heat capacity of water in joules per gram or per kilogram. The conversion factor depends on the definition adopted.”

Righto then.

So how do nutritionists measure the amount of calories in your thickshake?

First, they actually burn the food in a bomb calorimeter, which is a similar to a box with two chambers, one inside the other. The nutritionist will weigh a little bit of the food and put a sample of it onto a dish, and into the chamber of the calorimeter.

From Nutrition for Dummies “They fill the inner chamber with oxygen and then seal it so the oxygen can’t escape. The outer chamber is filled with a measured amount of cold water, and the oxygen in the first chamber (inside the chamber with the water) is ignited with an electric spark. When the food burns, an observer records the rise in the temperature of the water in the outer chamber. If the temperature of the water goes up 1 degree per kilogram, the food has 1 calorie; 2 degrees, 2 calories; and 235 degrees, 235 calories — or one 8-ounce chocolate malt!”

The argument from lots of nutritionists is that this is an inexact science, because who is to say that every human body burns calories in the same way. My body is always burning calories but does it burn more when I am awake, more in summer? More on Tuesday and less on Thursday?

I dislike kilojoules – we have this wrong in Australia. Switch to calories – oh fair country of mine!

Do you agree? Do you find kilojoules difficult to measure?

Great photo by chotda thanks


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