This study was published in the journal Cell Metabolism on Thursday and it revealed a molecular passage way in the brain that is controlled by insulin and it drives the added weight gain when someone is under stress.
"This study indicates that we have to be much more conscious about what we're eating when we're stressed, to avoid a faster development of obesity," said Herbert Herzog, head of the Eating Disorders laboratory at the Garvan Institute of Medical Research.
The researchers found that a molecule called NPY is at the center of the weight gain, and the brain produces it naturally when a person is stressed, and it stimulates eating in a person.
"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," said Kenny Chi Kin Ip, the study's lead author and a researcher at Herzog's lab.
When you eat, your brain is controlled by a part called the hypothalamus and another part called the amygdala is the one that processes emotional responses such as anxiety, according to the study.
The researchers found out that the nerve cells that are responsible for the production of NPY in the amygdala had receptors for insulin, which is a hormone that controls a person's food intake.
Normally, our body produces insulin after we eat and it helps the cells absorb glucose from our blood and sends a signal to the hypothalamus, the feeding center of our brain, to stop eating. The researchers discovered that stress alone can raise the blood insulin levels slightly but combining it with a high-calorie diet, the insulin levels showed it was 10 times higher and when we are stress free.
The high levels of insulin that are prolonged in the amygdala can cause the nerve cells to become immune to insulin, which can stop them from detecting insulin overall. The heightened NPY levels promote eating and it reduced the bodies' normal response to burn the stored energy through heat, creating a cycle.
"Our findings revealed a vicious cycle, where chronic, high insulin levels driven by stress and a high-calorie diet promoted more and more eating," concludes Prof. Herzog.
Overall, the research team was surprised about the significant effect of insulin, it shows that it does not only regulate functions in the body but it also affect pathways in the brain.
