WELCOME TO KILOJOULE SCHOOL
A (VERY) BRIEF HISTORY OF KILOJOULES
o, what are we talking about here? The calorie has been used as a dieting tool since the 1910s, though we switched to the metric measurement kilojoules – one calorie is 4.184 kJ – in Australia in the 1970s. Put simply, a calorie is a unit of energy, originally defined as the amount required to raise the temperature of 1g of water by 1°C. This is how the caloric value of food was measured: you’d burn it in a container surrounded by water, then note the temperature change. These days, a food’s kilojoule content is calculated by what’s called the Atwater system. This dictates that proteins and carbs contain 17 kilojoules per gram, while 1g of fat has 37 kilojoules. Work out a food’s macro balance and you can calculate
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