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Cooked food, calorie counts and food labels

Cooking food makes its calories more available, according to new research (subscription required) published this week in Proceedings of the National Academy of Sciences. The researchers fed diets of cooked or raw meat or sweet potato to lab mice, then watched the mice to see how much weight they gained on each diet. Changes in the animals' body weights clearly showed that cooked meat and cooked sweet potato provided more energy than their raw counterparts.

Media coverage of the study has focused mostly on what it means for our understanding of human evolution and on goofy references to cavemen gnawing on raw meat.

But what caught my eye about this study was something different. The method used to compare the calorie contents of cooked and raw food is quite different from the standard way of determining the calorie counts listed on food labels. And the study's findings imply that the standard method (known as the Atwater system) has some big flaws.

With the standard method, to measure the calorie content of, say, a piece of sweet potato, it's put in a tightly insulated chamber and then ignited. The amount of heat given off by the combustion is carefully measured and translated into an energy count in calories. The calculation does include some corrections for food components that aren't completely digested, such as fiber and protein, but the corrections are rough estimates. The method can't distinguish subtle differences in how a living body will handle two versions of the same food, prepared different ways.

Yet as we shift to eating entire diets that rely more and more on prepared foods (including foods prepared by industrial processes, not just at-home cooking) such distinctions may be increasingly important. I wonder if this will lead to a revamping of the calorie counts on food labels.

Previously: 40 years of changes in our food, Will redesigning food labels help consumers revamp their eating habits?, A call for understandable information on food labels and Repositioning nutritional information on food labels to encourage Americans to eat healthier
Photo by BBQ Junkie.
Via Science 360 News Service.

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