The results of a recent British study do link obesity with long-term stress. The researchers came to their conclusion after measuring the amount of the stress hormone cortisol in the hair of study participants. Cortisol is secreted by the adrenal glands in response to stress and also plays an important role in metabolism and determining where fat is stored.
Earlier studies have looked at cortisol levels in blood, saliva or urine, which tells you something about current stress but doesn’t reveal how long it has been going on. Also, these hormone levels fluctuate throughout the day and may reflect transient rather than chronic stress. According to the British team from University College London, hair cortisol is a better indicator.
More than 2,500 men and women age 54 or older participated in the study, and over the course of the investigation they provided hair samples twice. At intervals four years apart, the researchers cut a 2-centimeter lock of hair (slightly less than an inch long) from close to the scalp of each participant to measure cortisol levels. The hair had been growing for about 2 months. They also recorded the participants’ weight, body mass index (BMI) and waist measurement.
Results showed that the individuals with higher levels of cortisol in their hair had larger waist circumference and were more persistently overweight. Those classified as obese based on their BMI or waist circumference (more than 40 inches in men or 34.5 inches in women) had particularly high cortisol levels.
The findings don’t reveal whether chronically elevated cortisol levels are the cause of obesity or whether stress is a consequence of obesity. Also, because the study participants were older and almost all were white, the results might not apply to younger people and other ethnicities.
While these findings are interesting, I think it would be a mistake to blame all weight gain on cortisol. Heredity plays a role, as well, and the strongest influences are lifestyle factors, including eating habits, 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, and incorporate relaxation techniques into your daily routine. My 4-7-8 breathing exercise is the one I recommend. Perform it at least twice a day, and try it every time you feel anxious or upset.
Andrew Weil, M.D.
Sarah E. Jackson et al, “Hair cortisol and adiposity in a population-based sample of 2,527 men and women aged 54 to 87 years.” Obesity, February 23, 2017, doi: 10.1002/oby.21733