- Chronic stress has long been thought to be implicated in obesity.
- Cortisol is an hormone released in response to stress, and it plays an important role in metabolism and determining where fat is stored.
- Higher levels of cortisol accumulated over several months is associated with people being heavy and overweight.
People who suffer long-term stress may also be more prone to obesity.
The research by scientists at UCL involved examining hair samples for levels of cortisol, a hormone which regulates the body's response to stress.
‘Higher levels of cortisol in the hair is directly related to having larger waist circumference measurements, being overweight and having a higher body mass index (BMI).’
Stress has been always been associated with a variety of physical and mental health problems including high blood pressure, heart disease, a suppressed immune system, and sleep trouble.
Also stress has been considered to play a role in obesity as stressed people tend to report overeating and comfort eating foods high in fat, sugar and calories.
Chronic stress causes the release of stress hormone cortisol which plays an important role in metabolism and determining where fat is stored.
Study shows that chronic exposure to higher levels of cortisol over several months is associated with people being more heavy and more persistently overweight.
Previous studies have failed to examine effects of long-term cortisol levels in the blood. Instead, they linked obesity to the measurements of the hormone in blood, saliva or urine which are highly variable.
For the current study, 2,527 men and women aged 54 years and older were recruited. They were followed for four years.
The scientists took a lock of hair 2cm long from each participant which was cut as close possible to the scalp. This represented approximately two months of hair growth and they were tested for accumulated levels of cortisol.
In addition, the participants' weight, body mass index and waist circumference were examined.
In addition, and how hair cortisol related to the persistence of obesity over time were also evaluated
Results showed that people who had higher levels of cortisol present in their hair had larger waist circumference measurements, were heavier, and had a higher body mass index (BMI).
Those participants who were categorized as being obese or overweight, depending on their BMI or waist circumference, had higher levels of cortisol in their hair.
"These results provide consistent evidence that chronic stress is associated with higher levels of obesity," said Dr Sarah Jackson (UCL Epidemiology and Public Health) who led the research. "People who had higher hair cortisol levels also tended to have larger waist measurements, which is important because carrying excess fat around the abdomen is a risk factor for heart disease, diabetes, and premature death."
"Hair cortisol is a relatively new measure which offers a suitable and easily obtainable method for assessing chronically high levels of cortisol concentrations in weight research and may therefore aid in further advancing understanding in this area." Jackson added.
The major limitations of the study were the inclusion of only whites and that it was done in an older population in whom the levels of cortisol may differ relative to younger adults.
More research is needed to identify the link between cortisol level and obesity and if link is proved, then targeting cortisol levels may offer a new method for treating obesity.
The paper is published in the journal Obesity
- Sarah Jackson et al. Hair cortisol and adiposity in a population-based sample of 2,527 men and women aged 54 to 87 years. Obesity; (2017) DOI: 10.1002/oby.21733