If you’re having trouble losing weight, the problem might not be what you’re eating but rather how stressed you’re feeling. Researchers have found that people exposed to chronic stress are more likely to be overweight or obese.
Scientists have long thought that chronic stress may play a role in obesity. People tend to overeat and scarf down comfort foods high in fat, sugar, and calories when they’re anxious. Plus, the stress hormone cortisol is involved in the build up of abdominal fat.
This new study, published in the journal Obesity, confirms the link between long-term stress and the tendency to be overweight.
Past studies that investigated the link between cortisol and obesity primarily measured levels of this hormone in blood, saliva, or urine. These measurements can vary according to the time of day and other factors. Measuring cortisol in those ways also does not allow researchers to evaluate levels of this hormone over the long term.
In the current study, scientists from University College London (UCL) tested cortisol levels in hair samples from 2,527 men and women aged 54 and older participating in the English Longitudinal Study of Ageing, which gathered data over four years. The study authors cut a lock of hair 2 cm long from as close to the subjects’ scalp as possible. This amounted to two months’ growth and allowed them to measure cortisol levels over that same time.
The researchers also measured the participants’ weight, body mass index, and waist circumference then compared the hair cortisol levels to the persistence of obesity over time.
People whose hair cortisol levels were highest were more likely to have larger waist circumference measurements, were heavier, and had a higher body mass index (BMI).
Hair cortisol levels were especially high in participants considered obese according to their BMI or waist circumference.
“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.”
Limitations to this study included the gathering of data from an older population whose cortisol levels may differ from younger people. Additionally, subjects were was almost exclusively white.
More research is necessary to say for sure whether chronically elevated cortisol levels are a cause or a consequence of obesity. However, if they prove to be a cause, lowering cortisol levels may be an effective way to treat obesity.
Source: Sarah E. Jackson, Clemens Kirschbaum, Andrew Steptoe. Hair cortisol and adiposity in a population-based sample of 2,527 men and women aged 54 to 87 years. Obesity. 2017;25(3):539 DOI: 10.1002/oby.21733