Food for thought: comfort eating a myth

Subjects in experiment did not binge-eat after being put under pressure, even if they had an eating disorder

Scientists have found that there is no link between stress and binge-eating. The discovery promises to overturn decades of established thinking on the triggers for people with eating disorders. Cambridge University scientists were surprised to find that women suffering from either anorexia or bulimia ate less than a group of control subjects in their study when exposed to stress in the form of mental arithmetic problems and mild electric shocks.

“COMFORT eating” is a myth, according to a study that found no link between stress and binge-eating.

The discovery promises to overturn decades of established thinking on the triggers for people with eating disorders.

Twenty-two women with anorexia, 33 with bulimia and 30 healthy control subjects were asked to perform mental arithmetic exercises while being given small electric shocks.

They were then invited to an “all you can eat” buffet at Cambridge University’s eating behaviour unit.

Scientists were surprised to find that women suffering from either anorexia or bulimia ate less in general than the controls.

Published in the Journal of Neuroscience, the findings challenge the theory of binge-eating, which is that stress causes difficulty with self-control.

Despite its prominence, the theory has never been tested directly in patients until now, the authors said.

Dr Margaret Westwater, who led the research, said: “The theory suggests that these women should have eaten more when they were stressed, but that’s actually not what we found.

“Clearly, when we’re thinking about eating behaviour in these disorders, we need to take a more nuanced approach.”

Using blood biomarkers taken from the patients at various stages during the experiment, the team established that those with anorexia had raised levels of ghrelin, a hormone that tells the body it is hungry, when stressed.

However, at the same time there were also raised levels of peptide tyrosine tyrosine, a satiety hormone.

In patients with bulimia, there were no differences in levels of either hormone.

During their stay at the eating behaviour unit, the women received a controlled meal each morning provided by a nutritionist, before undergoing a fasting period during which they performed tasks while their brain activity was monitored using a functional MRI scanner.

The first tasks involved stopping the progression of a bar rising up a computer screen by pressing a key.

To raise their stress levels, the women were then asked to carry out a series of mental arithmetic tests while receiving mild but unpredictable electric shocks.

They were told that if they failed to meet the performance standard, their data would be dismissed from the study.

They were given feedback throughout the task, such as “your performance is below average”.

The women then repeated the stopsignal task again.

Once the tasks had been completed – but while the volunteers might still be expected to be in a heightened state of stress – they were offered the buffet.

Prof Paul Fletcher, joint senior author at the department of psychiatry, said: “It’s clear from our work that the relationship between stress and binge-eating is very complicated. It’s about the

‘When we’re thinking about eating behaviour in these disorders, we need to take a more nuanced approach’

environment around us, our psychological state and how our body signals to us that we’re hungry or full.

“If we can get a better understanding of the mechanisms behind how our gut shapes those higher order cognitive processes related to self-control or decision making, we may be in a better position to help people affected by these extremely debilitating illnesses.

“To do this, we need to take a much more integrated approach to studying these illnesses.”

Anorexia and bulimia are largely differentiated by body mass index, with adults with a BMI of less than 18.5kg/m2 classed as anorexic.

More than 1.6million people in the UK are thought to have an eating disorder, three quarters of whom are women.

Research last year found that eating disorders were soaring, with almost 20,000 people a year being admitted to NHS hospitals, amid concern that social media was fuelling a growing crisis.