Can obesity and stress influence appetite?

It’s all in your head.

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Obesity can result from excess intake in response to environmental food cues, and stress can drive greater intake and body weight. A new study by Johns Hopkins Medicine used fMRI to determine how stress might increase appetite in obese and lean adults.

By analyzing brain activity across networks in the brain, scientists found that stress impacts the brain’s responses to food and that both lean and obese adults react to food cues in areas of the brain associated with reward and cognitive control.

Data from 29 adults—16 women and 13 men—were evaluated for the study, of whom 17 were obese, and 12 were lean. Participants completed two fMRI scans following a combined social and physiological stress test.

During both scans, participants underwent a food word reactivity test. This experiment examined how people’s brains responded to food-related words, such as menu items written on a chalkboard. The scientists asked participants to envision each food’s appearance, aroma, and flavor and how it would feel about eating it right then and there, about stimulating the brain’s appetitive response. To understand how individuals made decisions regarding different foods, they were also asked how much they liked each food and whether they thought they should avoid eating it.

Lead researcher Susan Carnell, Ph.D., associate professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine, said“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.”

“The study also showed that stress impacts brain responses to food. For example, obese individuals showed greater activation of the orbitofrontal cortex, a brain reward region, after the stress test. We also found evidence for links between the subjective stress experienced and brain responses in both groups. For example, lean individuals who reported higher stress following the test showed lower activation of the dorsolateral prefrontal cortex, a key brain area for cognitive control.”

Journal Reference:

  1. Carnell S, Benson L, Papantoni A, Chen L, Huo Y, Wang Z, et al. (2022) Obesity and acute stress modulate appetite and neural responses in food word reactivity task. PLoS ONE 17(9): e0271915. DOI: 10.1371/journal.pone.0271915
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