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There's just something about being stressed that makes that juicy cheeseburger look even more delicious. We've all felt the irresistible pull of "comfort food" when stress is running high, and most of us have given into it—but science is finding more reasons why we should double our resolve to resist.
Case in point, a new animal study has found that eating more calories when stressed may result in gaining more weight than eating the same amount under less stress.
Searching for the brain mechanisms that control weight gain, researchers used a mouse model to trace the interplay of brain activity involved in stress-eating vs eating in a relatively stress-free environment, finding that high-calorie stress-eating sets off a “vicious cycle” of weight gain.
“Our study showed that when stressed over an extended period and high-calorie food was available, mice became obese more quickly than those that consumed the same high-fat food in a stress-free environment,” said Kenny Chi Kin Ip, an eating disorder specialist and lead author of the study, according to a press release.
At the center of the cycle is a molecule produced in the brains of mice and humans called Neuropeptide Y (NPY). The molecule appears not only in the hypothalamus, the brain area typically associated with regulating appetite and weight gain, but also in the amygdala, the epicenter of emotional response.
“We discovered that when we switched off the production of NPY in the amygdala, weight gain was reduced. Without NPY, the weight gain on a high-fat diet with stress was the same as weight gain in the stress-free environment,” Dr. Ip said. “This shows a clear link between stress, obesity, and NPY.”
Digging deeper, the researchers found that nerve cells producing NPY in the amygdala serve as “docking stations” for another hormone that plays an integral role in regulating calorie intake—insulin. Our bodies produce insulin after we eat, resulting in glucose absorption and eventually a “stop eating” signal sent to the hypothalamus. When all systems are functioning normally, this process works well.
When under stress, insulin production increases a little. But when extra stress was combined with stress-eating, this study found that insulin levels were 10 times higher in the stressed mice compared to those eating with less stress.
The result, according to the researchers, was that nerve cells in the brains of the stressed mice (especially in the amygdala and hypothalamus) eventually became desensitized to insulin, and also increased the production of NPY, which prompted even more overeating.
“Our findings revealed a vicious cycle, where chronic, high insulin levels driven by stress and a high-calorie diet promoted more and more eating,” said Herbert Herzog, head of the Eating Disorders Laboratory at the Garvan Institute of Medical Research and the lead of this research team. “This really reinforced the idea that while it’s bad to eat junk food, eating high-calorie foods under stress is a double whammy that drives obesity.”
This was an animal study so we can't say with certainty that the results would replicate in humans, but the same brain mechanisms and hormones are involved in both mice and humans. At a minimum, the research supports caution about something we already know isn't a healthy habit, and these findings may indicate that stress eating is even less healthy than we thought.
The study was published in the journal Cell Metabolism.
© David DiSalvo
