journalism

 I saw this interesting study on the energetics of cooking meat and tubers on NPR this morning. But I was aghast at the differences between the NPR reporting and the actual study. According to NPR:

So modern-day omnivores can rejoice in the fact that a simple hamburger is a beautifully engineered energy delivery system. But they should also remember that those little Harvard mice grew plump dining on tiny gourmet burgers from Julia Childs's butcher. "The mice were eating meat from Savenor's," Carmody says, "while I was eating meat from the local bodega."
 

So the mice grew plump on an all-meat diet? Hmm, let's pull up the study, evilly paywalled by PNASty even though they are supposed to be open access since it's an "early edition":

Maybe I'm reading this wrong, but considering that all the mean changes to body mass are in the minus zone, I'm not seeing any plump mice here. The researchers say:

Effects of Food Processing on Meat Diets. To assess the energetic impact of food processing, it was necessary to maintain mice on a 100% meat diet for a measurable period. Mice of this species (M. musculus) readily consume meat, and in some ecological contexts, they have been observed to inflict intensive predation pressure on vertebrate populations (16). Nevertheless, pure meat diets are not expected to be beneficial for omnivorous species. In humans, lean meat diets that derive a majority proportion of their calories from protein lead to rabbit starvation, a condition of negative energy balance resulting from the high costs of protein digestion and the limited capacity of the liver for urea synthesis (25, 26). We, therefore, expected mice to lose body mass on all experimental meat diets, with relative loss of body mass indicating the relative values of the underlying diets.

Although mice lost weight on all diets, we observed that cooking but not pounding had a positive effect on energy gain (2 × 2 RM ANOVA; cooking: P < 0.001, pounding: P = 0.138) (Fig. 3)

Hmm, NPR are you biased or what? 

I'm pretty sure that feeding the mice this evolutionarily inappropriate diet based on pretty lean meat would have resulted in their deaths had the experiments continued.

The study is somewhat interesting even though it is limited by the use of mice rather than people, because it underscores the fact that cooked food is more caloric than raw food. Sometimes I see people put "ground meat (raw)" in their fitday even though they made cooked hamburgers, which leads to an inaccurate caloric count. Evolutionarily the researchers conclude:

First, the adoption of cooking would have helped ancestral humans thrive. Meat and tubers have been exploited by humans for at least 2 million y, and the energetic resources of these foods are believed to have provided critical support for the evolution of costly increases in activity, birth rate, body size, and brain size (34). Meat would have been a preferred food, but its pursuit would require a large energetic investment with low rates of success (35). Tubers, by contrast, were less preferred but more consistently available, and this consistency would have made investments in the high-risk pursuit of meat possible (36). The proportions of animal and plant foods consumed by ancestral humans are unknown, but the parallel effects of cooking that we found suggest that the adoption of cooking would have led to energetic gains whether meat or tubers predominated. Moreover, because we found the effects of cooking to be incremental to the effects of pounding for both foods, the adoption of cooking was likely advantageous even if pounding methods were already in widespread use.

Some questionable stuff even here. The low rates of success for hunting is based on studies on modern hunter-gatherers. There is some evidence that game was much richer in the Early and Middle paleolithic.