Individuals affected by eating disorders such as anorexia nervosa or bulimia do not increase their food intake when under stress, according to research led by a team at the University of Cambridge.
Until recently, the prevailing theory suggested binge eating in individuals with an eating disorder was linked to an inability to self-regulate when under stress. The study, published in the Journal of Neuroscience, used MRI scans to directly test this theory in patients for the first time.
More than 1.6 million people in the UK have an eating disorder, three-quarters of whom are women. People who experience bulimia and some of those who experience anorexia nervosa share binge eating and associated vomiting symptoms.
The researchers analysed the behaviour of 85 women, 22 with anorexia nervosa, 33 with bulimia nervosa and 30 healthy controls. The women stayed at an eating behaviour unit for two days, where their diet and environment were strictly controlled. They underwent regular MRI scans to monitor brain activity whilst performing various tasks, some of which were designed to be stress-inducing.
On completion of the tasks, the women were taken to a relaxing lounge and offered an ‘all-you-can eat’ buffet and told they could eat as little or as much as they wanted.
Dr Margaret Westwater, who led the research while a PhD student at Cambridge’s Department of Psychiatry, said: ‘The idea was to see what happened when these women were stressed. Did it affect key regions of the brain important for self-control, and did that in turn lead to increases in food intake? What we found surprised us and goes counter to the prevailing theory.’
Stress did not affect the eating patterns of either the patient group or the control group. It also had no effect on the ability of either group to complete the tasks. However, the MRI scans revealed that each group recorded different brain activity when under stress.
Dr Westwater added: ‘Even though these two eating disorders are similar in many respects, there are clear differences at the level of the brain. In particular, women with bulimia seem to have a problem with pre-emptively slowing down in response to changes in their environment, which we think might lead them to make hasty decisions, leaving them vulnerable to binge-eating in some way.’
Professor Paul Fletcher, a joint senior author at the Department of Psychiatry, added: ‘It’s clear from our work that the relationship between stress and binge-eating is very complicated. 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.’