Stress can override natural fullness cues, leading to increased food consumption and sweet desires. When you’re anxious, a high-calorie snack may seem like a good way to unwind. However, this combination has a negative side effect. According to Sydney scientists, stress paired with calorie-dense ‘comfort’ food causes brain alterations that lead to greater eating, increased desires for sweet, highly appealing foods, and excess weight gain.
The Garvan Institute of Medical Research discovered that stress overrode the brain’s natural reaction to satiety, resulting in nonstop reward signals that drive the consumption of more highly desirable food. This occurred in the lateral habenula, a region of the brain that normally dampens these reward signals when aroused.
“Our findings show that stress can override a natural brain response that reduces the pleasure gained from eating, implying that the brain is constantly rewarded to eat,” explains Professor Herzog, senior author of the study and Visiting Scientist at the Garvan Institute.
“We demonstrated that chronic stress, when combined with a high-calorie diet, can lead to increased food intake as well as a preference for sweet, highly palatable foods, promoting weight gain and obesity. This study emphasizes the importance of a balanced diet during times of stress.”
The research was published in the journal Neuron.
We demonstrated that chronic stress, when combined with a high-calorie diet, can lead to increased food intake as well as a preference for sweet, highly palatable foods, promoting weight gain and obesity. This study emphasizes the importance of a balanced diet during times of stress.
Professor Herzog
From stressed brain to weight gain
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. To understand what drives these eating habits, the team investigated in mouse models how different areas in the brain responded to chronic stress under various diets.
“We discovered that an area known as the lateral habenula, which is normally involved in turning 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 reward signals to remain active and encourage feeding for pleasure while 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.”
The researchers discovered that at the centre of the weight gain was the molecule NPY, which the brain produces naturally in response to stress. When the researchers blocked NPY from activating brain cells in the lateral habenula in stressed mice on a high-fat diet, the mice consumed less comfort food, resulting in less weight gain.
Driving comfort eating
The researchers next conducted a’sucralose preference test,’ in which mice were given the option of drinking water or chemically sweetened water.
“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,” according to Herzog. “Crucially, we did not see this preference for sweetened water in stressed mice that were on a regular diet.”
Stress overrides healthy energy balance
“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.
According to the researchers’ results, stress is a major regulator of eating patterns that can override the brain’s natural ability to balance energy demands.
“This research emphasises just how much stress can compromise a healthy energy metabolism,” said 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.”
