Food labels are essentially wrong. The calorie counting system on food labels around the world goes as far back as the late 19th century. It espouses the calculation of the ‘energy content of various foods by burning small samples in controlled conditions and measuring the amount of energy released in the form of heat.’ Based on this system, carbohydrates and protein are estimated to provide an average of 4 kcal per gram, while fat provides 9 kcal per gram. Such a measurement, known as metabolizable energy, has ‘been the currency of food ever since.’

What is missing in this calorie accounting system is the variable of digestion. ‘And digestion – from chewing food to moving it through the gut and chemically breaking it down along the way – takes a different amount of energy for different foods.’

Here lies the calorie delusion contained in food labels. ‘In the case of the brownie versus the muesli bar, the label will overestimate the calories derived from the fibre and protein-packed muesli bar, perhaps by enough to make it lower in calories than the brownie. Just 20 kcal per day more than you need can add up to roughly a kilogram of fat over a year.’

In 2002, the UN Food and Agriculture Organization (FAO) convened an international panel of nutrition experts ‘to investigate the possibility of recommending a change to food labelling standards to reflect the cost of digestion.’ The group generally ‘decided to stick with metabolizable energy for calculating nutrition labels on food products because, “the problems and burdens ensuing from such a change would appear to outweigh by far the benefits”.’ The nutrition experts concluded, “We believe that metabolizable energy is a more accurate representation of what’s in that food for everybody [and is] more accurate for the purposes of food labeling.”

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Via New Scientist