Results: Death of the calorie

Some people's intestines are 50% longer than others: those with shorter ones absorb fewer calories, which means that they excrete more of the energy in food, putting on less weight. Did you ever consider this fact before this survey?

Here'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 digestible calories in beef rises by 15% on cooking, and in sweet potato some 40% (the exact change depends on whether it is boiled, roasted or microwaved). So significant is this impact that Richard Wrangham, a primatologist at Harvard University, reckons that cooking was necessary for human evolution. It enabled the neurological expansion that created Homo sapiens: powering the brain consumes about a fifth of a person's metabolic energy each day (cooking also means we didn't need to spend all day chewing, unlike chimps). Did you ever consider this fact as important when you were thinking about weight control?

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. Did you try this?

Different parts of a vegetable or fruit may be absorbed differently too: older leaves are tougher, for example. The starchy interior of sweetcorn kernels is easily digested but the cellulose husk is impossible to break down and passes through the body untouched. Just think about that moment when you look into the toilet bowl after eating sweetcorn. Can you mention any other food as hard to digest as the cellulose husk from sweetcorn?