Cortisol is a hormone secreted by the adrenal glands in response to stress, and research does suggest that there may be a tie between cortisol levels in women and the accumulation of excess weight in the abdominal area. A study at Yale University in 2000 compared stress reactions among women who had a high waist-to-hip ratio (because their fat tended to be in the belly) with those among women with a low waist-to-hip ratio (indicating more fat storage in the hips than the waist).
The researchers noted that diseases caused by high levels of cortisol (Cushing's Syndrome is one) are characterized by excessive amounts of fat in the abdominal area, an unhealthy distribution that increases the risk of high blood pressure, heart disease, and diabetes. In addition to the link to weight gain, elevated cortisol levels can have adverse effects on the immune system, memory, and sugar metabolism.
In the Yale study women were given tests (involving puzzles and speech designed to stimulate stress) to see how they responded. The researchers found that women with a high waist-to-hip ratio, whether they were overweight or slim, secreted more cortisol under stress and also reported more stress in their daily lives than women with low waist-to-hip ratios. Results of the study were published in the September/October 2000 issue of Psychosomatic Medicine.
As far as caffeine is concerned, a study published in the July/August 1998 issue of Psychosomatic Medicine showed that caffeine can elevate levels of cortisol and another stress hormone, ACTH (adrenocorticotropic hormone) in men prone to high blood pressure as well as in men at low risk for this disease. I doubt that caffeine has much impact on weight gain as a result of any effect on cortisol levels.
While these findings are interesting, it would be a mistake to blame all weight gain on cortisol. Heredity plays a role, too, as well as such lifestyle factors as smoking, alcohol consumption and lack of exercise. If you want to decrease the impact of stress in your life, which may result in lower cortisol levels, be sure to get regular exercise and sufficient sleep. Incorporate meditation and relaxation techniques into your daily routine. My breathing exercise will help bring calmness throughout your body. Do it at least twice a day, and try it every time you feel anxious or upset.
Andrew Weil, M.D.