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Phoenix666 [soylentnews.org] writes:

More than two-thirds of American adults are overweight or obese [arstechnica.co.uk]. For many of them, the cure is diet: one in three are attempting to lose weight in this way at any given moment. Yet there is ample evidence that diets rarely lead to sustained weight loss. These are expensive failures. This inability to curb the extraordinary prevalence of obesity costs the United States more than $147 billion in healthcare, $4.3 billion in job absenteeism, and even more in lost productivity.

At the heart of this issue is a single unit of measurement—the calorie—and some seemingly straightforward arithmetic. “To lose weight, you must use up more calories than you take in,” according to the Centers for Disease Control and Prevention. Dieters like Nash and Haelle could eat all their meals at McDonald’s and still lose weight provided they burn enough calories, says Marion Nestle, professor of nutrition, food studies, and public health at New York University. “Really, that’s all it takes.”
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After visiting over 40 US chain restaurants, including Olive Garden, Outback Steakhouse and PF Chang’s China Bistro, Susan Roberts of Tufts University’s nutrition research center and colleagues discovered that a dish listed as having, say, 500 calories could contain 800 instead. The difference could easily have been caused, says Roberts, by local chefs heaping on extra french fries or pouring a dollop more sauce. It would be almost impossible for a calorie-counting dieter to accurately estimate their intake given this kind of variation.

Even if the calorie counts themselves were accurate, dieters like Haelle and Nash would have to contend with the significant variations between the total calories in the food and the amount our bodies extract. These variations, which scientists have only recently started to understand, go beyond the inaccuracies in the numbers on the back of food packaging. In fact, the new research calls into question the validity of nutrition science’s core belief that a calorie is a calorie.

Using the Beltsville facilities, for instance, Baer and his colleagues found that our bodies sometimes extract fewer calories than the number listed on the label. Participants in their studies absorbed around a third fewer calories from almonds than the modified Atwater values suggest. For walnuts, the difference was 21 per cent. This is good news for someone who is counting calories and likes to snack on almonds or walnuts: he or she is absorbing far fewer calories than expected. The difference, Baer suspects, is due to the nuts’ particular structure. “All the nutrients—the fat and the protein and things like that—they’re inside this plant cell wall.” Unless those walls are broken down—by processing, chewing or cooking—some of the calories remain off-limits to the body, and thus are excreted rather than absorbed.

Not all calories are created equal.

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