ENERGY IN: FOOD
Energy Input – Diet
Most people are aware that the energy input from food is determined in general by the amount of food consumed.
However, its determination is much more complicated than, say, for a vehicle which consumes just a single fuel, generally gasoline (petrol) or diesel. The fuel for humans comprises thousands of different types with varying energy content.
Consequently, food energy input has to be evaluated by measuring the quantity of each food item consumed, in grams, and multiplying by its energy content per gram.
The procedure is to analyse in detail your actual input. The question transforms to: what exactly do you eat?
Listing what you actually eat is instructive in itself and can be an eye-opener: one can delude oneself about consuming a balanced diet.
Standard Daily Amount of Energy (SDA): ten megajoules (10 MJ)
Instead of directly using the kilojoule as the food energy unit, utilising a reference number – a standard daily amount of energy – makes for an easier method of evaluation of food energy content.
A Standard Daily Amount of Energy (SDA) proposed here, is 10000 kJ or 10 megajoules (10 MJ); it corresponds to the traditional guideline daily amount of 2500 kcal for the average adult male.
In percentage terms, 100% SDA is 10000 kJ and 1% SDA is 100 kJ.
All food energy inputs are in terms of percentages:
a yogurt is 4%
a 40 g slice of bread is 4%
an apple is 1.5%
a glass of wine is 5%
and so on.
So, a simple procedure is to work in percentages, which is an intuitive measure for most people, but are actually hundreds of kilojoules (the yogurt serving quoted, is 400 kJ).
The SDA percentage figures are read directly from the energy content values in hundreds of kilojoules.
The current EU front of package display does show the energy content of a serving as a percentage (based on 2000 kcal): 5% in the yogurt example. The SDA percentages are 1/5 less.
US packaging presents the energy content only in "Calories" per serving, i.e. about 100 "Calories" in the yogurt example. Just multiply the hundreds figure by four to get the SDA%.
For a day, total energy input on a restricted diet might be: 10% for breakfast; 20% at mid-day; and 30% in the evening; a total of 60% SDA or six megajoules (1 + 2 + 3 = 6 MJ).
The theme: As easy as 1-2-3 or 10-20-30.
For more on:
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Energy Content
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Food Energy Information:
Packaging
European Union
United States
Website databases
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Current Energy Input – Diet
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Diet structure
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