Antiquated and inaccurate methods for calculating the caloric content of foods leads to erroneous consumer decisions, according to a recent New Scientist article on ”The Calorie Delusion: Why Food Labels Are Wrong”. Specifically, “according to a small band of researchers, using the information on food labels to estimate calorie intake could be a very bad idea. They argue that calorie estimates on food labels are based on flawed and outdated science, and provide misleading information on how much energy your body will actually get from a food. Some food labels may over or underestimate this figure by as much as 25 per cent, enough to foil any diet . . .”
Caloric estimates worldwide are grounded upon 19th century testing methods which “calculated 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,” then subtracted waste products from estimated caloric content. But, of course, “nutritionists are well aware that our bodies don’t incinerate food, they digest it. 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. According to Geoffrey Livesay, an independent nutritionist based in Norfolk, UK, this can lower the number of calories your body extracts from a meal by anywhere between 5 and 25 per cent depending on the food eaten. ‘These energy costs are quite significant,’ he says, yet are not reflected on any food label.”
For many useful examples and illustrations of considerable relevance, see the article. But note also that in this and in a subsequent article, “The Burning Truth About Calories”, New Scientist observes that, despite their known inaccuracy, the UN Food and Agricultural Organization opposes revising the methods for calculating calories, and opposes relabeling foods. New Scientist and the majority of nutritionists seem to agree with the FAO, for reasons which I personally find unpersuasive at best. See what you think.