Chronic stress makes the mind desire for comfort food

Source: Garvan Institute of Medical Research

Summary: Chronic stress can suppress the body’s natural satiety signals, increasing appetite and boosting desires for sweets.

Chronic stress suppresses the brain’s normal satiety-inducing reaction, resulting in continuous reward signals that encourage the consumption of more appetizing food.

This happens in an area of the brain known as the lateral habenula, which normally blocks these reward impulses when it is active.

Professor Herzog, the study’s principal author and visiting scientist at the Garvan Institute, comments, “Our findings 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.

From mental stress to weight gain:

While some people choose to eat less than usual during stressful times, most people choose calorie-dense, high-sugar, and fatty foods.

To understand what drives these eating behaviours, the team examined how different brain regions responded to long-term stress under varying diets in mouse models.

“We discovered that an area known as 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 are chronically stressed, this part of the brain remains silent — allowing the reward signals to stay active and encourage feeding for pleasure, no longer responding to satiety regulatory signals,” explains first author Dr Kenny Chi Kin Ip from the Garvan Institute.

“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.”

Researchers discovered that the primary cause of weight gain was the chemical NPY, which the brain normally produces in response to stress.

Stress mice on a high-fat diet consumed fewer comfort foods and gained less weight when the researchers prevented NPY from activating brain cells in the lateral habenula.

Next, in a “sucralose preference test,” the mice were offered the choice of drinking water or water that had been artificially sweetened by the investigators.

“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,” says Professor Herzog.

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

Chronic Stress outweighs a balanced, healthy energy level.

“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,” says Professor Herzog.

Stress is a major regulator of eating habits that can override the brain’s natural ability to balance energy needs, according to the study.

“This research emphasises just how much stress can compromise a healthy energy metabolism,” says Professor Herzog. “It’s 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.”