Calories were ditched in favour of kilojoules within the field of nutrition over 40 years ago, but their popularity in diet circles has seen this old Imperial unit endure. If you haven’t quite made the switch in your mind from calories to kilojoules, we’ve simplified everything here so you’ll be able to read a label from a glance and prepare healthy and balanced, kilojoule-controlled meals with ease.
Here’s the deal. 1 Calorie = 4.184 kilojoules.
Although everyone’s daily kilojoule requirements will vary depending on their size, muscle mass and activity levels, on average, women aged between 19 to 50 years of age who lead fairly sedentary lifestyle (at an office desk) should be consuming around 7500 kilojoules per day to maintain their current weight (more specific recommendations can be made by a Fernwood food coach).
To make sense of these numbers, it can help to think of how you could spread out your kilojoule consumption over the course of a day. For example, three main meals and three smaller snacks between meals each day could look like this: 2000 + 500 + 2000 + 500 + 2000 + 500 = 7500kJ
1 kilogram of body fat contains the equivalent of 37,000kJ.
So to lose weight, you need to create a deficit of 37,000kJ.
One way to do this is through exercise. For example, 13 hours of running at 8km an hour will burn 37,000kJ. How you break this up doesn’t matter; half an hour on the treadmill every day for just under a month will get you there.
Another way to create a kilojoule deficit is through making more sensible food choices. For example, if you were to swap a breakfast of two pieces of toast with butter, for one piece of toast with butter and a hard-boiled egg, within two months you will have created a deficit of 37,000 kilojoules and lost one kilogram. Making these little swaps can really add up over time.
If your aim is to lose weight, you could start to restructure your daily intake into three lower-kilojoule main meals and just two snacks per day, which could look like: 1500 + 500 + 1500 + 500 + 1500 = 5500kJ.
By creating a deficit of 2000 kilojoules per day, you will have reached a deficit of 37,000 kilojoules and lost 1 kilograms in 18 days.
So for the best weight loss results, the combination of healthier eating with regular exercise can’t be beaten.
A note on alcohol
Don’t be fooled by its translucent liquid form, alcohol has almost as many kilojoules per gram as fat.
Consider this: 1 gram of alcohol has 29kJ, just 8kJ shy of fat, which has 37kJ per gram.
The reason we always refer to alcohol as ‘empty kilojoules’ is because it has such a high energy content – almost double that of carbs (16kJ/g) and protein (17kJ/g) – without providing any of the nutrients or satiating benefits of actual food.
What’s more, drinking alcohol dampens our judgement and can make us crave the wrong types of food. So those high-salt, fatty canapés we were able to resist when sober become so much more difficult to turn away.
If you’re serious about losing those last few kilos, cut back on your alcohol consumption, or cut it out altogether.