15 July 2009

Dietary fibre is one example. As well as being more resistant to mechanical and chemical digestion than other forms of carbohydrate, dietary fibre provides energy for gut microbes, and they take their cut before we get our share.

Errors in the Atwater factors for protein and fibre are just one reason why the brownie may pack more of a calorific punch than the label suggests. The brownie will be much softer in texture than the nut-bar, a factor that is known to lower the energy cost of digestion….

What’s more, the brownie is made from refined sugar and flour, making it easier for our bodies to extract the available calories than it would be from the complex carbohydrates of the oatmeal in the cereal bar. And while the Atwater system assumes that the proportion of food that passes through the gut undigested is more or less constant, at around 10 per cent, we have known for more than 60 years that this is not the case. Thirty per cent or more of coarse-ground wheat flour may be excreted, while today’s finely milled flours may be almost completely digested. As a result, foods made from these fine flours - like that brownie - are likely to channel practically all of the energy from carbohydrate into the body.

Cooking, too, can affect how many calories the body gets from foods, another factor the Atwater system ignores, says Richard Wrangham, a biological anthropologist at Harvard University. Wrangham became interested in the impact of food processing on calorie availability as part of his work into how cooking affected human evolution. In his recently published book Catching Fire: How cooking made us human, Wrangham suggests that the advent of cooking propelled our ancestors onto the evolutionary fast track, by providing more energy to invest in growing bigger brains.

via The calorie delusion: Why food labels are wrong - health - 15 July 2009 - New Scientist.

Fascinating article discussing the limits of the current nutritional labeling system when it comes to calorie counting. It does not, however, discuss the broader issue of the types of calorie sources (carbs vs. fat) or food types (dark leafy greens vs. carrots vs. processed meat).  The article concludes that though these limits have been known for a while, it is unclear if the cost and confusion of overhauling the current system would significantly increase people’s ability to choose the healthier food.

I did weight watchers before my wedding and was able to lose weight using their ball park points-counting system.  I either looked up the food I ate in a table or took account of calories, fat, and fiber.  That approach worked for me, but made home-cooked meals difficult to gauge in value.

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