Chronic stress fuels the consumption of palatable food and can enhance obesity development. While stress- and feeding-controlling pathways have been identified, how stress-induced feeding is orchestrated remains unknown.
Scientists from Sydney claim that stress and calorie-dense ‘comfort’ foods alter the brain to encourage overeating, increase the desire for sweet, highly appealing foods, and result in weight gain.
The brain’s normal response to satiety was overridden by stress, according to a study from the Garvan Institute of Medical Research, which resulted in constant reward signals that encouraged consuming more highly appetizing food. This happens in the lateral habenula, a region of the brain that, when active, generally muffles these reward signals. The findings reveal that stress can override a natural brain response that diminishes the pleasure gained from eating – meaning the brain is continuously rewarded for eating.
Professor Herzog, a senior author of the study and Visiting Scientist at the Garvan Institute, said, “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.”
Some people may eat less under stress, but most will eat more than usual and select calorie-dense foods high in sugar and fat.
The scientists used mouse models to study how various brain regions responded to chronic stress under varied diets to understand what motivates these eating behaviors.
First author, Dr. Kenny Chi Kin Ip from the Garvan Institute, said, “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 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.”
“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 scientists found that the chemical NPY, which the brain naturally creates in reaction to stress, was at the root of the weight increase. In stressed mice fed a high-fat diet, the researchers inhibited NPY from activating brain cells in the lateral habenula. As a result, the mice consumed fewer comfort foods and gained less weight.
The scientists next conducted a “sucralose preference test” in which they gave mice the option of drinking either water or water that had been artificially sweetened.
Professor Herzog said, “Stressed mice on a high-fat diet consumed three times more sucralose than mice 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 on a regular diet.”
“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, stress appears to change the equation, driving eating that is bad for the body long term.”
Journal Reference:
- Chi Kin Ip, Jemma Rezitis et al. The critical role of lateral habenula circuits in the control of stress-induced palatable food consumption. Neuron. DOI: 10.1016/j.neuron.2023.05.010