SOMETIMES, the only thing holding our sanity together on a stressful day is a string of fatty and sugary snacks, aka comfort food. But a new study, conducted in mice, provides more evidence that stress eating — especially of high calorie meals — leads to more weight gain than eating while, well, not stressed. Chronic stress turns on a key mechanism in the brain that prompts mice to keep eating, a group of researchers reported today (April 25) in the journal Cell Metabolism.
The team analysed the behaviour and weight gain of a group of mice. Researchers chronically stressed some of the mice by isolating them from other mice and replacing their bedding with a thin layer of water. The other mice were placed in typical, non stressful living conditions. The researchers fed some of the mice in each group chow and others a high fat diet.
After two weeks, the investigators found that the stressed mice that ate the healthy chow showed no difference in body weight compared with unstressed mice. However, the stressed mice that ate high calorie food gained more weight than the non-stressed mice that ate the same, high calorie food. Researchers found that this difference was, in part, because the stressed mice ate a lot more than their chill counterparts.
The investigators then peered into the mice brains to try to figure out the reasons for these differences. The hypothalamus, a tiny area in the center of the brain (in both mice and humans), controls appetite and hunger, whereas the nearby amygdala controls emotional responses, such as anxiety and stress, according to a statement. Both the amygdala and the hypothalamus produce a molecule called neuropeptide Y (NPY) in response to stress. In the hypothalamus, this molecule is known to stimulate food intake.
Following a hunch that this molecule could be driving the additional weight gain linked to stress, the researchers turned off the process that produces NPY in mice. When they blocked the ability of the amygdale to make this molecule in mice, the researchers found that the stressed and non-stressed mice on a high calorie diet gained about the same amount of weight. This suggests that NPY does, in fact, drive the increased weight gain associated with stress eating. That effect of NPY may involve an interaction with insulin. It turns out that these NPY molecules have docking stations for that hormone, which the body uses to control how much food mice (and humans) eat.
