Why chronic stress pushes us to eat more and worse and becomes a vicious circle

Accompanying the mid-morning coffee with a donut, attacking the bag of chips in the aperitif or surrendering to the lasagna when you get home from work can seem like small rewards immersed in a stressful work day.. However, recent research indicates that they are a very bad choice, and not only from a nutritional point of view, but also because they promote a vicious circle that, in the long run, modulates brain responses and from which it can be very difficult to break out.

This is the main conclusion of a study carried out by the group of Herbert Herzog, director of the Eating Disorders laboratory at the Garvan Institute of Medical Research, in Sydney (Australia).

In animal models, scientists have described how chronic stress overrides the brain's natural response to satiety, causing the pleasure one derives from food to decrease, and instead favors an increase in signals seeking “reward” , which translates into a hedonistic race towards the intake of more and more appetizing foods.

Thus, the research, the results of which have just appeared in the journal Neuron, shows that exposure to stress influences the functioning of a part of the brain, the lateral habenula, which when activated tends to dampen reward signals.. But when you add a hypercaloric diet, the result is a greater preference for sweet and appetizing foods, and, in the long run, weight gain and obesity.

The authors are emphatic: “Chronic stress encourages the consumption of appetizing foods and can promote the development of obesity,” they write in this article whose first author is Chi Kin Ip, from the Garvan Institute.

Speaking to this medium, Professor Herzog explains that normally, the brain's responses to a diet rich in fat and to stress are channeled through different neural pathways.. On the one hand, “a long-term high-fat diet leads to an adjustment of homeostatic regulatory pathways that reduce the impulse to eat and, at the same time, increase energy consumption, mainly by increasing the basal metabolic rate and the production of heat to counteract the excess supply of energy”.

And, on the other hand, “stress, in an acute context, promotes increased energy consumption to immediately cope with the stressful (dangerous) situation.”

The malicious alliance arises when the “dangerous” situation becomes chronic: “In a chronic context, stress modulates the hedonic energy homeostasis system, which is powerful enough to override the normal homeostatic control mechanism that normally prevents overeating.”. In summary, the scientist states by email, “in a chronic context, stress is the dominant partner”,

This vicious cycle is orchestrated in the brain by the neuropeptide NPY, a molecule that the body produces naturally in response to stress.. When the researchers blocked NPY in the lateral habenula cells of stressed mice fed a high-fat diet, the animals consumed less food, and weight gain slowed.

How to break that circle

Can NPY be used to develop treatments that promote satiety? Although it is highly conserved in evolution and is identical between mice and humans, as well as the neural pathways that control it, confirms Professor Herzog, this molecule involved in eating and stress “is also involved in the regulation of many other functions such as thermoregulation and heart rate”, making it difficult to use as a therapeutic target.

However, it points to a much simpler and more accessible option to break this vicious circle.

According to the study, stressed mice fed a high-fat diet consumed three times more sucralose (a sweetener) than mice fed a high-fat diet alone.. However, they did not observe such a preference for sugar water in stressed mice that were on a normal diet.

So the researcher points out that the study “is a reminder that you have to avoid a stressful lifestyle and, above all – if you suffer from long-term stress – try to follow a healthy diet and avoid junk food.”