The Economist: Death of the calorie. “For more than a century we’ve counted on calories to tell us what will make us fat. Peter Wilson says it’s time to bury the world’s most misleading measure.”
“There’s a further weakness in the calorie-counting system: the amount of energy we absorb from food depends on how we prepare it. Chopping and grinding food essentially does part of the work of digestion, making more calories available to your body by ripping apart cell walls before you eat it. That effect is magnified when you add heat: cooking increases the proportion of food digested in the stomach and small intestine, from 50% to 95%.
The difficulty in counting accurately doesn’t stop there. The calorie load of carbohydrate-heavy items such as rice, pasta, bread and potatoes can be slashed simply by cooking, chilling and reheating them. As starch molecules cool they form new structures that are harder to digest. You absorb fewer calories eating toast that has been left to go cold, or leftover spaghetti, than if they were freshly made. Scientists in Sri Lanka discovered in 2015 that they could more than halve the calories potentially absorbed from rice by adding coconut oil during cooking and then cooling the rice. This made the starch less digestible so the body may take on fewer calories (they have yet to test on human beings the precise effects of rice cooked in this way). That’s a bad thing if you’re malnourished, but a boon if you’re trying to lose weight.”
I read this article last week and was reminded of it by this MetaFilter post that has more links on the subject.