Study | Effects of Stress on Appetite


A woman sits with no appetite at a table with food | Image by Shutterstock

Researchers at Johns Hopkins Medicine are shedding light on the role stress plays in determining one’s appetite.

In a study published last month in the journal PLOS ONE, researchers found that activity in the areas of the brain responsible for reward and cognitive control varies depending on stress levels, claiming stress impacts how both lean and obese adults respond to “environmental food cues.”

Researchers analyzed fMRI scans of their test subjects as they thought about and considered a range of different food items.

The study sample included 16 women and 13 men. Of the 29 individuals, 17 were obese, and the remaining 12 were lean.

During the study, researchers tried to intensify their subjects’ brain activity by prompting them to imagine the look, smell, and taste of each food being described. The subjects were also asked to describe how much they wanted or did not want a particular food.

The point of the experiment was to gain insight into what can shape food decisions.

While the sample size was small, it revealed potential differences in how obese and lean individuals perceive food.

Lead researcher Susan Carnell stated, “The experiments showed that obese and lean adults differ somewhat in their brain responses, with obese adults showing less activation of cognitive control regions to food words, especially to high-calorie foods, like for example, grilled cheese.”

Stress also impacted participants differently, according to the study. Following “stress tests” in which subjects were led to believe they were being video recorded and had to react to food words while their hands were submerged in cold water, researchers found that obese subjects experienced higher activations of the orbitofrontal cortex, an area of the brain that perceives sensory rewards.

Food cues under stressful conditions neurologically primed the obese subject to have a greater appetite and less cognitive control over what they chose to eat following the stress tests.

While the results from the study help further scientific understandings of the relationship between stress and appetite, the researchers emphasized that more reproducible studies would need to be published.

One recent study out of the University of Texas Southwestern Medical Center in Dallas seemed to support Carnell’s findings.

As previously reported in The Dallas Express, researchers argued that obese adults’ increased risk of mortality due to COVID-19 likely led to greater anxiety and stress among that cohort, concluding that the increased anxiety was the most significant factor contributing to substantial weight gain in that group.

“The COVID-19 pandemic is a fascinating model for individual and social stress and showed that changes in mental health can really preclude people from maintaining a healthy body weight,” said lead researcher Jaime Almandoz.

Another study cited by Almandoz found that approximately 48% of U.S. adults gained weight during the pandemic.

Still, even before COVID-19, obesity weighed heavy on the country’s health system as the nation steadily put on the pounds and careened into an obesity epidemic.

According to the CDC, roughly 40% of American adults already qualify as obese, and nearly half of all adults are projected to be obese by 2030, per a study published in the New England Journal of Medicine, as previously reported by The Dallas Express.

Regardless, whether stress is driving American weight gain seems beside the point for North Texas, which, as recently as 2019, ranked one of the least stressed parts of the country but still ranks high for obesity.

Local dietician Isabella Ferrari of Doherty Nutrition told The Dallas Express recently that a lack of nutritional education, the “unwalkable” layout of the Dallas-Fort Worth Metroplex, and people valuing convenience over healthy habits are key factors driving obesity in North Texas.

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