"Humans are not bomb calorimeters, of course, and we don't extract every calorie from the food we eat."
"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."
"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."
"Wrangham and his colleagues have since shown that cooking unlaces microscopic structures that bind energy in foods, reducing the work our gut would otherwise have to do. It effectively outsources digestion to ovens and frying pans. Wrangham found that mice fed raw peanuts, for instance, lost significantly more weight than mice fed the equivalent amount of roasted peanut butter. The same effect holds true for meat; there are many more usable calories in a burger than in steak tartare."
"Industrial food processing, which subjects foods to extremely high temperatures and pressures, might be freeing up even more calories. The food industry, says Wrangham, has been "increasingly turning our food to mush, to the maximum calories you can get out of it. Which, of course, is all very ironic, because in the West there's tremendous pressure to reduce the number of calories you're getting out of your food."
"None of this means that the calorie is a useless concept. Inaccurate as they are, calorie counts remain a helpful guide to relative energy values: standing burns more calories than sitting; cookies contain more calories than spinach. But the calorie is broken in many ways, and there's a strong case to be made for moving our food accounting system away from that one particular number. It's time to take a more holistic look at what we eat."
"One option is to focus on something other than energy intake. Like satiety, for instance. Picture a 300 calorie slice of cheesecake: it is going to be small. "So you're going to feel very dissatisfied with that meal," says Susan Roberts. If you eat 300 calories of a chicken salad instead, with nuts, olive oil and roasted vegetables, "you've got a lot of different nutrients that are hitting all the signals quite nicely," she says. So you're going to feel full after you've eaten it. That fullness is going to last for several hours."
Full article here - arstechnica.com/science/