How a brain switch could combat comfort food cravings during stress

By Mark Waghorn

Comfort food cravings could be stopped by flicking a switch in the brain that is turned on by stress, according to new research.

People often turn to fatty and sugary snacks like crisps, sweets and biscuits when they feel under pressure.

And it's a vicious circle - creating changes in gray matter that drive more eating and excess weight gain.

They occur in an area called the lateral habenula, which plays a key role in inhibiting urges.

Experiments found anxiety overrode natural responses to satiety, leading to non-stop reward signals that promote highly palatable treats.

First author Dr. Kenny Chi Kin Ip, from the Garvan Institute in Sydney, Australia, said: "We discovered the lateral habenula, which is normally involved in switching off the brain's reward response, was active in mice on a short-term, high-fat diet to protect the animal from overeating.

"However, when mice were chronically stressed, this part of the brain remained silent – allowing the reward signals to stay active and encourage feeding for pleasure, no longer responding to satiety regulatory signals."

He added: "We found that stressed mice on a high-fat diet gained twice as much weight as mice on the same diet that were not stressed."

The study, published in the journal Neuron, identifies stress as a critical regulator of eating habits that can block the brain's natural ability to balance energy needs.

Senior author Professor Herbert Herzog said: "This research emphasizes just how much stress can compromise a healthy energy metabolism.

"It is a reminder to avoid a stressful lifestyle, and crucially – if you are dealing with long-term stress – try to eat a healthy diet and lock away the junk food."

While some people eat less during times of stress, most will eat more than usual and choose calorie-rich options high in sugar and fat.

The findings open the door to developing an anti-obesity pill that targets the lateral habenula.

Herzog said: "They reveal stress can override a natural brain response that diminishes the pleasure gained from eating – meaning the brain is continuously rewarded to eat.

“We showed that chronic stress, combined with a high-calorie diet, can drive more and more food intake as well as a preference for sweet, highly palatable food, thereby promoting weight gain and obesity.

"This research highlights how crucial a healthy diet is during times of stress."

The Australian team discovered that at the center of the weight gain was the molecule NPY, which the brain produces naturally in response to stress.

When they blocked the chemical from activating brain cells in the lateral habenula, stressed mice consumed less comfort food, resulting in less weight gain.

The researchers next performed a "sucralose preference test" – allowing mice to choose to drink either water or water that had been artificially sweetened.

Herzog said: "Stressed mice on a high-fat diet consumed three times more sucralose than mice that were on a high-fat diet alone, suggesting that stress not only activates more reward when eating but specifically drives a craving for sweet, palatable food.

“Crucially, we did not see this preference for sweetened water in stressed mice that were on a regular diet.”

The breakthrough offers hope for combating the obesity epidemic. The UK has been dubbed the 'fat man' of Europe, with nearly two-in-three adults overweight.

Herzog added: "In stressful situations, it’s easy to use a lot of energy and the feeling of reward can calm you down – this is when a boost of energy through food is useful.

"But when experienced over long periods of time, stress appears to change the equation, driving eating that is bad for the body long term."