By Kathleen Doheny
"We don't know which came first, the greater body weight or the higher cortisol," said researcher Andrew Steptoe. He's the British Heart Foundation professor of psychology at University College London.
For the study, Steptoe's team analyzed levels of cortisol in a lock of hair about three-quarters of an inch long, cut as close as possible to the scalp. This hair sample reflected accumulated cortisol levels over the previous two months, the researchers said.
Cortisol is the body's primary stress hormone, triggered when you have a "flight-or-fight" response to danger. It benefits you to escape danger, but if cortisol levels stay chronically high, it is linked to depression, weight gain, anxiety and other problems, according the Mayo Clinic.
The study included more than 2,500 adults in England, aged 54 and older.
The researchers compared cortisol levels in the sample to body weight, waist circumference and body mass index (or BMI, a rough measure of body fat based on height and weight measurements). They also looked at how cortisol levels related to persistent obesity.
Those participants with higher cortisol levels tended to have larger waist circumferences (over 40 inches for men, over 35 inches for women and a risk factor for heart disease and other problems). People with higher cortisol levels also had higher BMIs -- the higher the BMI, the higher the levels of body fat.
Higher cortisol levels were also tied to greater obesity levels that persisted over the four years examined.
Although the study found an association between cortisol and obesity, it did not prove a cause-and-effect link.
One U.S. expert also questioned the method used in the study. Currently, "the evidence for using hair samples as a weight or obesity predictor is lacking," said Connie Diekman. She's director of university nutrition at Washington University in St. Louis.
The study researchers noted that using hair cortisol is a relatively new measure that's easily obtainable and may help in researching the topic.
The link between cortisol and obesity was found for both genders. "In this study, we did not see any difference between men and women," Steptoe said.
Nor did the researchers find age differences among those studied. The average age of the volunteers was 68. However, since all the men and women were older, the same results may not be the same in younger adults, Steptoe said.
From the study, the researchers couldn't tell whether higher cortisol levels triggered stress eating, leading to obesity, but nutrition and weight experts know that many who are stressed do overeat.
"Managing stress eating is complicated," Diekman said, "and what works for some does not work for others."
She suggested maintaining a regular meal schedule. That reduces blood sugar drops that can trigger overeating.
"Do not eat right from a bag or box," Diekman said. "Always put food on a plate."
When you eat, avoid doing anything else, Diekman advised. Instead of checking email, watching television or movies or working, focus on the food.
The study was published Feb. 23 in the journal Obesity.