In an interview with NPR, Daniel Lieberman, professor of evolutionary biology at Harvard, discussed his new book, The Story of the Human Body: Evolution, Health and Disease, shedding light onto exactly how our bodies deal (or don't deal) with 21st century stresses.
Ever wonder why you crave mac and cheese or other comfort foods after an especially stressful day at the office? It actually has to do with cortisol levels, Lieberman reveals, and how they affect blood sugar. When you get really stressed, your body releases cortisol — it makes you more alert and able to combat danger. BUT, it also makes you crave high-energy (read: high-calorie) foods to replenish all the calories your body thinks it will burn while fending off said danger.
And, since these days our stressful events tend to have more to do with stressful jobs than with stressful lions, we're not really burning off calories while stressed-out, just consuming them after. This, coupled with the fact that we experience chronic stress, rather than the quick, situational stresses of the Paleo era, means that cortisol levels are elevated for far longer than Mother Nature intended them to be.
For more on our mysterious caveman origins, check out the entire interview. (NPR)