Scientists have revealed why feeling stressed keeps you reaching for donuts, candy, and even candy bars.
Australian researchers have said that when someone is full, an area of the brain kicks in to turn off reward signals from food that signal them to stop eating.
But in experiments on stressed mice, they found this area remained silent prompting the rodents to keep eating for pleasure. Those in the stressed group gained twice as much weight as mice in the non-stressed group.
The scientists said their study highlights the importance of sticking to a healthy diet, particularly when suffering from chronic stress.
Australian researchers have warned that stress may promote comfort eating (stock image)
Dr Herbet Herzog, an eating disorder researcher at the Garvan Institute of Medical Research in Sydney, said: “Our findings reveal that stress can override a natural brain response that decreases the pleasure gained from eating, meaning the brain is continually rewarded for eating.
“We have shown that chronic stress, combined with a high-calorie diet, can drive ever-increasing food intake as well as a preference for sweet and highly palatable foods, thereby promoting weight gain and obesity.”
“This research highlights how critical a healthy diet is during times of stress.”
In the study, published today in the journal Neuron, the scientists divided mice into two groups and monitored the amount of food consumed.
Each was offered the same high-fat diet for a short period of time and was able to eat as much as they wanted.
One group of mice was kept under laboratory conditions, while the other was subjected to chronic stress.
The scientists didn’t say how this was accomplished, but in previous cases it has involved hanging mice by their tails for an extended period until they stopped struggling. This is repeated to trigger chronic stress.
The researchers found that mice in the stressed group gained twice as much weight as mice on the same diet that weren’t stressed.
Tests revealed that an area of the brain known as the lateral habenula, which is located near the thalamus, remained silent when the mice were stressed.
In unstressed mice, this area lit up once they were full signaling them to stop eating.
But for those who were chronically stressed, the area was not activated by satiety, prompting them to continue eating.
To consolidate the results, the scientists also performed a ‘sucralose preference test’.
This was when the mice were given two options, potable water or water that had been artificially softened.
They found that the stressed mice consumed three times more sucralose than those fed only a high-fat diet.
The researchers said that at the heart of this response was a molecule called NPY, which the brain naturally produces in response to stress.
When the researchers blocked NPY in stressed mice with a high-fat diet, the mice ate less comfort food and gained less weight.
Dr. Herzog added: “In stressful situations, it’s easy to use up a lot of energy, and the feeling of reward can calm you down.
“This is when an energy boost through food comes in handy.”
“But, when experienced over long periods of time, stress appears to change the equation, driving harmful eating to the body in the long run.”
He added: “This research underscores how stress can impair healthy energy metabolism.
“It’s a reminder to avoid a stressful lifestyle, and more importantly, if you’re dealing with long-term stress, try to eat a healthy diet and put junk food to the side.”
The scientists didn’t take into account other factors that could also drive stressed eating in the mice, such as an interrupted sleep schedule.
It was unclear whether the results of these experiments in mice were directly translatable to humans.
The research was funded by the National Health and Medical Research Council of Australia.
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