Research done by scientists at UCL, which involved examining hair samples for levels of the hormone cortisol, indicates that people who suffer from long-term stress may also be more prone to obesity. Cortisol regulates the body’s response to stress.
The paper’s findings were published in the journal Obesity and showed that exposure to high levels of cortisol for more than a few months is associated with people being more both more heavily and more persistently overweight. It has long been hypothesized that chronic stress is implicated in obesity. People are inclined to report ‘comfort eating’ and overeating of foods high in sugar, fat and calories in times of stress. The stress hormone cortisol plays a significant role in determining where fat is stored and metabolism.
Previous studies investigating the link between obesity and cortisol relied primarily on measurements of the hormone in saliva, blood, or urine. These levels may vary considerably depending on the time of day and other situational factors. These studies did not capture long-term cortisol levels.
More than two and a half thousand women and men aged 54 and older participated in the study. Data was collected over a four-year period in the English Longitudinal Study of Ageing. In the study, scientists took a lock of hair 2cm long cut as close possible to a person’s scalp from each participant. This represents about two months’ worth of hair growth with its associated accumulated levels of cortisol. The researchers also noted the participants’ weight, body mass index and waist circumference. The data was then correlated to determine how hair cortisol related to the persistence of obesity over time.
The results show that people with higher levels of cortisol present in their hair tended to be heavier, have larger waist circumference measurements and have a higher BMI (body mass index). Individuals classified as obese based on their BMI being greater than 30, or waist circumference (more than 102cm in men and 88cm in women) had predominantly high levels of hair cortisol.
Dr Sarah Jackson of the UCL Epidemiology and Public Health department led the research. She noted that the results of this research provide consistent evidence that higher levels of obesity is associated with chronic stress. She added that people with higher hair cortisol levels also tended to have larger waist measurements. This is important, as carrying excess fat around the belly is a known risk factor for diabetes, heart disease and premature death.
Measuring hair cortisol is a relatively new method, which offers an easily obtainable and suitable method for evaluating chronically high levels of cortisol concentrations in weight research. It is possible that this technique will therefore assist in advancing understanding in this area further.
The study had limitations, which included the fact the data was from an older population where levels of cortisol may differ relative to younger adults. The sample was also almost exclusively white. It is also not known whether chronically elevated cortisol levels are a consequence, or a cause of obesity.