Sarah Jackson
development related to autism may occur before birth. These findings are clearly inconsistent with vaccines as a cause of autism.
But none of this emerging research seems to have dampened the fires burning within the anti-vaccine movement. I could resurrect Edward Jenner and Jonas Salk for joint TED talks about the benefits of vaccination, and somehow I doubt it would make any difference at this point. Despite Kennedy’s disingenuous plea for evidence of safety, it’s not evidence he really cares about. If it were, he could find more than enough for free.
But if either De Niro or Kennedy read this article and change their mind, I’m happy to take the $100 000 anyhow. – Washington Post THE world is getting fatter, and it’s making us sicker. But could rising stress levels be playing an important role in our growing waistlines?
Obesity is now one of the leading causes of death worldwide and is associated with increased risk of developing a host of chronic health conditions. There is great public interest in why some people struggle with their weight while others find it easy to stay slim, with blame attributed to genes or conditions such as thyroid problems.
Stress is another potential risk factor that has attracted research attention. People tend to report overeating and “comfort eating” foods that are high in sugar, fat and calories when stressed. And because the stress hormone cortisol plays a role in metabolism and fat storage, there are plausible biological mechanisms behind a possible link between stress and putting on weight.
In research published in Obesity recently, chronic stress was consistently linked with people being heavily, and persistently, overweight.
Data was collected over a fouryear period as part of the English Longitudinal Study of Ageing, a study that follows a large group of people aged 50 and older. People who had higher levels of cortisol in their hair tended to have a larger waist circumference, were heavier, and had a higher body-mass index (BMI). People classified as obese on the basis of their BMI ( 30) or waist circumference ( 102cm in men, 88cm in women) had particularly high levels of cortisol in their hair.
Why was hair used to measure cortisol levels? Previous studies looking at the link between cortisol and obesity have relied mainly on measurements of the hormone in OBESITY: The world is getting fatter, and it’s making people sicker. blood, saliva or urine which may vary according to the time of day and other “situational factors”, such as diet or illness. Because these methods give a very short-term picture of a person’s stress levels, these studies were not able to evaluate the relationship between obesity and longer-term stress. The distinction between acute (short-term) and chronic (longer-term) stress is important because the former is thought to serve as a protective fight or flight response, whereas the latter can have a damaging effect on the body.
Over the past decade, a new method for measuring cortisol levels in hair has been developed, and has been shown to be a reliable way of assessing chronic stress exposure.
A lock of hair 2cm long was taken from each participant, cut as closely as possible to the scalp. Hair grows at an average rate of 1cm per month, so samples represented about two months’ growth with associated accumulated levels of cortisol.
People’s weight, height and waist circumference were measured, and used to assess the relationship between levels of hair cortisol and adiposity (fatness).
It cannot be determined from research that stress is causing people to become obese, but if causation can be proved through further investigation, the link between chronic stress and obesity offers a potential target for interventions aimed at preventing and treating obesity. Stress-reduction techniques such as meditation and yoga are cheap, accessible options that could help people reduce their risk of developing obesity. It may also be possible to use drugs that reduce cortisol levels to treat obesity in more severe cases.
Jackson is a research psychologist, Health Behaviour Research Centre, University College London.