Cooking our food allows us humans to actually obtain more net energy from our food because we don't have to send hours gnawing at a hunk of raw meat or processing leafy greens. The anthropologist described two studies to back up his story. The first paper he alluded to was a study (Oka et al., 2003) of two groups of rats. Group 1 was fed normal pellets and group 2 was fed a softer, air puffed version of the same pellet. Both group were fed the same total number of Calories and all results were normalized to exercise. At the end of 26 weeks, it turns out that the soft food group was (statistically) significantly fatter than the control. The post-eating temperature of the soft-fed rats were lower than the hard-fed, suggesting that the metabolism of the hard-fed rats is 'working harder.' The conclusions drawn by the actual researchers and the NPR dude from this experiment are slightly different. The rat guys hypothesize that the different in weight comes more from neurological cues from the act of eating the different textured pellets and Mr. NPR says that the lower temperature comes from the little rat body not having to work as hard to process the softer pellet. I find both interpretations interesting.
The second scientific article (Evenepoel et al., 1999) that is mentioned was slightly more relevant to the argument that cooking food changes the caloric energy that is obtained by humans from food. The researchers in the study labeled eggs and tracked them through human digestion and determined the amount of protein absorbed by the small intestines as a function of whether or not the egg was cooked. There was a 30% difference in the amount of protein that escaped digestion within the small intestine between the two eggs, with the cooked egg having almost 95% of labeled proteins digested in the small intestine. This brings up the question of what cooking food actually does to the nutritional or energy value of foods. According to this thinking, the old dogma of 'a calorie is a calorie is a calorie' does not quite hold up. Cooking may change the amount of net energy we get from food whether the caloric discrepancy comes from our metabolism working harder with uncooked foods or that the energy from the harder to metabolize raw food isn't processed during the relatively short time it is in our digestive tract.
So what does all this mean? Well as with all science, especially science covered in the media, these results and hypotheses should be taken with a grain of salt. What I take from this discussion is an affirmation that we need to be more cognizant of what we eat and how we eat it. I am by no means at all saying that we should al be on the "raw foods diet." Our bodies evolved to eat cook food and we need it to get the energy necessary to function properly (as mentioned in the podcast, women on the "raw foods diet" often stop menstruating because they do not get sufficient energy from their diet). I do think, however, that we need to cut back on the processed foods and let our bodies do some of the processing. Those mashed up, freeze dried carrots that are puffed into chip like things are probably not as good for your body as an unprocessed carrot, period. Anyways, I thought this was interesting food for thought.