A hand pressing down on a hamburger, a typical comfort foodShare on Pinterest
Feeling stressed may trigger cravings for comfort foods. Marta Mauri/Stocksy
  • Eating comfort food when stressed switches off the brain region that stops you from over-eating, according to a new study.
  • Under normal circumstances, this region neutralizes the chemical reward one gets from eating, making it less enjoyable.
  • The phenomenon makes sense in wild animals, including non-modern humans, promoting a quick intake of energy in response to a threat.
  • However, it is less helpful in today’s world, where stress is less often directly related to survival.

For people who are stressed, it may seem as if comfort food offers the ideal — and maybe only — quick fix. A new study in mice from the Garvan Institute of Medical Research in Sydney, Australia suggests, however, that those people should think twice before tucking into a treat.

The study finds that the combination of stress and comfort food switches off the brain’s mechanism for letting one know when they have had enough to eat.

This can lead to an over-indulgence in one’s comfort food of choice, as well as weight gain and obesity, potentially sources of yet more stress.

The brain area affected is the lateral habenula, an organ that exists in both mice and humans. Under normal conditions, the region produces a mild, unpleasant sensation in the short-term presence of a high fat diet, switching off the brain’s reward response, thus making further eating less pleasurable. Many comfort foods are high in fat.

Working with chronically stressed mice, the researchers found that the lateral habenula remained uncharacteristically silent as high fat foods were being eaten. The mice kept eating, apparently for pleasure, without becoming satiated.

Upon further analysis, the researchers discovered that after giving stressed mice a calorie-free sweetened food pellet, they consumed twice as much sweetened food pellet (or liquid) than non-stressed mice. This demonstrates that a preference for sweets — even if calorie-free — persisted in the stressed mice.

Confirming their finding, when the researchers re-activated the lateral habenula using optogenetic light that can control neuronal activity, the mice stopped over-eating.

The study is published in Neuron.

If eating comfort food as a response to stress can lead to weight gain, can it be a sensible personal strategy?

From an evolutionary perspective, according to the study’s lead author Dr. Chi Kin Ip of the Garvan Institute of Medical Research, yes, it can be.

“Eating behavior is probably the most critical behavior that is conserved across all species to support survival,” he said.

Dr. Ip said that animals living in the wild lack the privilege of over-indulging in high fat food sources and that their stress systems allow them to survive by fine-tuning their energy use and supply depending on current demands.

High fat foods provide a way to gain energy quickly, and as Dr. Ip put it, “having more energy in the body is certainly better in the wild than having less energy.”

In modern humans, stress is less relevant to our literal survival.

Addressing concerns about weight gain from stress eating, Dr. Rennis said, “Indulging in comfort foods occasionally does not pose a problem.”

On the other hand, Dr. Tomiyama explained, “We do know that higher weight is extremely stigmatized in this country, and I’ve spent a decade of research showing that weight stigma is stressful and stimulates a biological stress response.”

Dr. Rennis noted that over-eating comfort food in response to stress is “similar to drinking alcohol occasionally to wind down. It’s okay once in a while, but can lead to problems if done in excess.”

Dr. Tomiyama pointed out that comfort foods do not necessarily have to be high in sugar, fat, or calories to be comforting.

“We… have a study where we trained people to feel better after eating fruit,” she said.

Asked about the likelihood that a mouse study produced results that would also apply to humans, both Dr. Ip and Dr. Tomiyama felt that it did.

“Humans are animals just like mice, and non-human animal studies provide really tight experimental control that provides valuable information we just can’t get in humans,” Dr. Tomiyama said.

Dr. Ip explained some of the similarities between humans and animals:

“The anatomical structure, as well as the function of the habenula, is highly conserved across all species, including humans. The lateral habenula is a region that plays a critical role in regulating emotional response. Under activation, it triggers an aversive behavior, which is one of the mechanisms that triggers emotional distress. However, when they are silenced, it induces the opposite, which is a reward response,” he said.

He noted further that a molecule identified in the study as being important to the behavior of the lateral habenula is also present in humans.

It is not entirely clear if there is a universal definition of comfort food, said Dr. A. Janet Tomiyama, who was not involved in the study.

“People assume comfort food is automatically high fat, high-sugar, high calorie foods,” she said, “but no one has systematically tested this.”

The general sense, however, said Dr. Lesley Rennis, who was also not involved in the study, is that “comfort food is food that tastes good and makes us feel good. Typically, it is calorie-dense, rich in sugar and fat, and often has nostalgic and sentimental value.”

“Sometimes called hyper-palatable foods, these foods are rewarding and stimulate the release of feel-good hormones like serotonin.”
— Dr. Lesley Rennis

Much research has investigated the psychological appeal of comfort foods. Dr. Rennis said the study adds to the conversation.

“It provides a layer of knowledge regarding the physiology of stress and its impact on food intake. Like all states of disease, there are both physiological and psychological contributors to stress eating,” she said.