Orexin neurons are cells in the brain that produce the signalling molecule orexin, which is linked to anxiety and stress. Scientists at the Francis Crick Institute have discovered that these cells are inactivated by eating.
They suggest that this may be a reason people eat more when they feel anxious or stressed.
Furthermore inactivation of orexin neurons is linked to weight gain - although this can be reversed by minor dieting.
Denis Burdakov of the Crick led the study, which was carried out in mice. The mice were allowed to eat normally while the researchers used fiber photometry, a technique for recording brain cell activity, to see what happened to their orexin cells as they ate.
The activity of these cells decreased within milliseconds of the mice starting to eat and stayed lower the whole time they were eating. This was irrespective of what the mice ate, and happened even when they were eating liquid and calorie-free types of food.
Lars Fugger's team at the Weatherall Institute of Molecular Medicine at the University of Oxford created transgenic mice that lacked orexin cells altogether. These mice overate and became overweight - although the researchers found that this weight gain was preventable by mild dieting.
This suggests that non-drug interventions may be useful for managing weight gain associated with reduced orexin signalling - or that eating (even calorie-free food) might be a way to head off anxiety disorders in people with overactive orexin cells.
"Further research into neuroscience-based lifestyle interventions for anxiety and obesity might lead to treatments that are easier to implement and have fewer side effects," say the scientists.
The paper, Inhibitory Interplay between Orexin Neurons and Eating, is published in Current Biology.