Binge eaters may be genetically predisposed to gorge on sweet and fatty foods, according to a study led by a York University researcher.
The study identifies significant genetic differences between obese individuals suffering from Binge Eating Disorder and obese individuals without the disorder.
It found that binge eaters possess a specific type of receptor in the brain opioid system that has been previously linked to drug and alcohol addiction. The study is the first to examine this gene in relation to obesity.
"Binge-eating individuals appear to have enhanced reactivity to the hedonic properties of food, such as its palatability and appearance," says study lead author Caroline Davis, professor of kinesiology in York’s Faculty of Health. "In other words, they appear to be more responsive to the pleasant taste of sweet and fatty foods, which proliferate in our current food environment."
The study examined genetic markers for brain dopamine and opioid systems in subjects aged 25 to 50. Scientists believe dopamine fosters the motivation to engage in rewarding behaviours – the "wanting" of reward, while opioids regulate the resulting pleasurable sensations we get from eating. Previous animal research has linked opioids to binge eating of fat.
Researchers found that binge eaters have a greater frequency of the A118G ("gain of function") allele of the mu-opioid receptor (OPRM1) gene. The study also showed binge eaters scored significantly higher on a self-report measure of hedonic eating.
Davis anticipates the research could lead to improved treatment strategies for those who suffer from the disorder. It also points to the need to reconsider how we carry out studies aimed at understanding the causes of overeating and weight gain, she says.
"Studies are typically designed whereby obese individuals are compared to non-obese participants in order to try and understand the causes of weight gain," says Davis. "In my view, it doesn’t make sense to consider obese individuals as a unified group. There are many different routes to obesity, so it behooves us as scientists to look at subtypes of the condition in order to get a clearer understanding of the diversity of causal mechanisms."
The study, "Dopamine for ‘Wanting’ and Opioids for ‘Liking’: A Comparison of Obese Adults With and Without Binge Eating," is forthcoming in the journal Obesity. The study was co-authored by researchers from the University of Toronto’s Centre for Addiction & Mental Health and the University Health Network.