A lot of time and effort have gone into determining calorie counts over the years. But new research suggests they may be wrong. More precisely, the research, done by Richard Wrangham of Harvard University, indicates cooking food increases its calorie count, possibly by as much as 25 to 50 percent. And he's not talking about the water-versus-fat issue dietician Jessica Cox mentioned in the previous section.
Wrangham asserts past scientists never considered the caloric cost involved in the digestive process. Your body spends a lot of energy digesting, say, a raw carrot or raw piece of beef. But if you cook these foods, they soften, and your body expends fewer calories digesting them. Thus, the net effect is that you've taken in more calories from a cooked meal of beef and carrots than from the raw version [source: Wrangham].
Another aspect of cooking food that past researchers overlooked concerns digestive enzymes. Our body can only digest what it can get its hands on. A raw potato, for example, has tightly packed starches that our digestive enzymes can't access. When cooked, however, those starches are gelatinized, releasing sugar-based molecules that our bodies can now feast upon, adding to our caloric intake. Similarly, cooking beef opens up its muscle proteins to our digestive enzymes. In addition, preparing food for cooking by chopping, grinding and the like also makes them more accessible to digestive enzymes [sources: Wrangham, You Beauty].
Wrangham and his associates also say their studies show the Atwater system for determining calories is flawed. For one thing, it ignores the bacteria in our stomach. When we eat food, our stomach's bacteria steal some of it to essentially feed themselves. Thus, less is left over for our body as a whole to take in, meaning we're getting fewer calories. The Atwater system also doesn't look at the effect of processing, assigning the same caloric value to, say, whole-grain wheat and highly milled flour. But since our bodies will use more energy digesting the whole-grain wheat, it should be assigned a lower caloric value.
Don't think this means a healthy diet should be composed of all raw foods, though. Yes, our bodies work harder to digest them, so eating a lot of raw foods means you're taking in fewer calories — definitely a bonus if you're trying to lose weight. But if you only eat raw foods, that can be problematic. One study Wrangham looked at showed those who ate a 100 percent raw-food diet were unhealthy. The average woman didn't have a functioning menstrual cycle, and half of the women stopped getting their period at all, suggesting they were taking in far too few calories. Moderation is the key, he says; a diet of both raw and processed foods is best.