Cortisol is a hormone that plays several very important roles in the human body. Many of these are health-promoting, under the right circumstances. Others can be disease-promoting, especially if cortisol levels are chronically elevated.
Among the disease-promoting effects of chronically elevated blood cortisol levels are that of excessive gluconeogenesis, causing high blood glucose levels even while a person is fasting. This also causes muscle wasting, as muscle tissue is used to elevate blood glucose levels.
Cortisol also seems to transfer body fat from subcutaneous to visceral areas. Presumably cortisol promotes visceral fat accumulation to facilitate the mobilization of that fat in stressful “fight-or-flight” situations. Visceral fat is much easier to mobilize than subcutaneous fat, because visceral fat deposits are located in areas where vascularization is higher, and are closer to the portal vein.
The problem is that modern humans often experience stress without the violent muscle contractions of a “fight-or-flight” response that would have normally occurred among our hominid ancestors. Arguably those muscle contractions would have normally been in the anaerobic range (like a weight training set) and be fueled by both glycogen and fat. Recovery from those anaerobic "workouts" would induce aerobic metabolic responses, for which the main fuel would be fat.
Coates and Herbert (2008) studied hormonal responses of a group of London traders. Among other interesting results, they found that a trader’s blood cortisol level rises with the volatility of the market. The figure below (click to enlarge) shows the variation in cortisol levels against a measure of market volatility.
On a day of high volatility cortisol levels can be significantly higher than those on a day with little volatility. The correlation between cortisol levels and market volatility in this study was a very high 0.93. This is almost a perfectly linear association. Market volatility is associated with traders’ stress levels; stress that is experienced without heavy physical exertion.
Cortisol levels go up a lot with stress. And modern humans live in hyper-stressful environments. Unfortunately stress in modern urban environments is often experienced while sitting down. In the majority of cases stress is experienced without any vigorous physical activity in response to it.
As Geoffrey Miller pointed out in his superb book, The Mating Mind, the lives of our Paleolithic ancestors would probably look rather boring to a modern human. But that is the context in which our endocrine responses evolved.
Our insatiable appetite for over stimulation may be seen as a disease. A modern disease. A disease of civilization.
Well, it is no wonder that heavy physical activity is NOT a major trigger of death by sudden cardiac arrest. Bottled up modern human stress likely is.
We need to learn how to make stress management techniques work for us.
Visiting New Zealand at least once and watching this YouTube video clip often to remind you of the experience does not hurt either! Note the “honesty box” at around 50 seconds into the clip.
Coates, J.M., & Herbert, J. (2008). Endogenous steroids and financial risk taking on a London trading floor. Proceedings of the National Academic of Sciences of the U.S.A., 105(16), 6167–6172.
Elliott, W.H., & Elliott, D.C. (2009). Biochemistry and molecular biology. 4th Edition. New York: NY: Oxford University Press.