[bronzeager]

This has very little to do with weight loss (in any way we can control) but I thought some here might be as tickled as I about this odd factoid I ran across, reading a paleoanthropology article for a class I'm teaching:

The metabolic cost of brain tissue is approximately 240 kcal/ kg/day and as such is considerably higher than certain tissues such as skeletal muscle (13 kcal/kg/day, at rest), similar to other organs such as the liver (200 kcal/kg/day), and lower than others such as the heart (440 kcal/kg/day) (Holliday, 1986; Elia, 1992). Given that humans and other primates (including great apes) have RMRs similar to other mammals (Leonard and Robertson, 1992, 1994; Aiello and Wheeler, 1995; Snodgrass et al., 2007) despite their relatively large brains, a comparatively large proportion of the resting energy budget is expended on brain metabolism in living humans (20–25%) and non-human primates (8–10%) compared to other mammals (3–5%) (Leonard and Robertson, 1994; Aiello and Wheeler, 1995).

(RMR = resting metabolic rate.) What this points out is that even if you are lying on the sofa, your brain is burning, proportionally, lots more of your daily calories than it would be if you were, say, a lemur lying on a sofa. And WAY more than if you were a badger lying on a sofa.* So pat your brain on the back today for the good job it's doing in your weight loss efforts.

*No offense intended to any lemurs or badgers who may be reading this.

From: J. Josh Snodgrass, William R. Leonard, Marcia L. Robertson, "The Energetics of Encephalization in Early Hominids," in The Evolution of Hominin Diets, 2009. (It's actually readable online at the Scribd website, if you are interested in hominid evolution.)

[Charmsey]

Whoa! That's Way interesting and I love it! Thanks for sharing...This makes me feel pretty good about life.

[JenMusic]

Nice to know! Makes me feel good for, you know, having a human-sized brain.

[Jesse Taylor]

I wonder if you can do stuff to increase that. That is cool.

[bronzeager]

Well, there are tradeoffs ... the authors go on to make the points that —

1) because of the energy needs of the large human brain, humans require a more energy-dense diet than other primates;*

2) humans have an increased ability, and need, to store body fat, in order to buffer the energy needs of the brain in times of food scarcity (you can't just shrink the big brain or put it into low gear to save energy, especially because you probably need it to find food);

3) this body fat storage ability is particularly prevalent in women and baby humans, because the big human brain in its early stages needs a continuous supply of nourishing fatty acids and glucose in order to develop properly;

4) the fact that humans have proportionally less skeletal muscle than other animals (this is true of other primates also apparently) may also compensate for the increased energy needs of the brain.

*Less-energy dense food DOES mean humans have more compact digestive systems, so they can have more svelte waists than other primates. Think about it: have you ever seen a gorilla with an hour-glass figure?