It's Only Natural: Our Innate Response to Stress continued...
When we experience something stressful, our brains release a substance known as corticotropin-releasing hormone (CRH), which puts the body on alert and sends it into "fight or flight" mode. As the body gears up for battle, the pupils dilate, thinking improves, and the lungs take in more oxygen. But something else happens as well: Our appetite is suppressed, and the digestive system shuts off temporarily. CRH also triggers the release of the hormones adrenaline and cortisol, which help mobilize carbohydrate and fat for quick energy. When the immediate stress is over, the adrenaline dissipates, but the cortisol lingers to help bring the body back into balance. And one of the ways it gets things back to normal is to increase our appetites so we can replace the carbohydrate and fat we should have burned while fleeing or fighting.
"But when was the last time you responded to stress with such physicality?" Peeke asks. In today's modern world, this elegant survival mechanism may be an anachronism that causes the body to refuel when it doesn't need to.
Yet, it's not just quick, unsettling episodes that can prove problematic, says Peeke. Feeling stressed-out over a long period of time may be fattening, too: Sustained stress keeps cortisol, that cursed hunger promoter, elevated and that keeps the appetite up, too.
And there's another factor as well. If stress and cortisol levels stay high, so will insulin levels, says Robert M. Sapolsky, PhD, a professor of biological sciences and neuroscience at Stanford University. "The net effect of this will be increased fat deposition in a certain part of the body."
And that body part generally is the waistline. A recent study conducted by researchers at Yale University and published in the September 2000 issue of Psychosomatic Medicine compared 30 women who stored fat primarily in their abdomens with 29 women who stored it mostly in their hips. They found that the women with belly fat reported feeling more threatened by stressful tasks and having more stressful lives. They also produced higher levels of cortisol than the women with fat on their hips. And that, the authors reasoned, suggests that cortisol causes fat to be stored in the center of the body.