Australian researchers have discovered a new molecular pathway in the brain that triggers more weight gain in times of stress.
A team led by Professor Herbert Herzog, Head of the Eating Disorders laboratory at the Garvan Institute of Medical Research, Sydney, discovered in an animal model that a high-calorie diet, when combined with stress, resulted in more weight gain than the same diet caused in a stress-free environment.
The researchers revealed a molecular pathway in the brain, controlled by insulin, which drives the additional weight gain. They will publish their findings in the journal Cell Metabolism on April 25, 2019 (EST).
“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,” Professor Herzog said.
The brain’s comfort-food ‘control centre’
To understand what controls ‘stress eating’, the Garvan researchers investigated different areas of the brain in mice. While food intake is mainly controlled by the hypothalamus, another part of the brain – the amygdala – processes emotional responses, including anxiety.
“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,” lead study author Dr Kenny Chi Kin Ip said.
Crucial to this weight gain, the scientists discovered, was a molecule called NPY. The brain produces NPY naturally in response to stress in order to stimulate eating in humans as well as mice.
“We discovered that when we switched off the production of NPY in the amygdala, weight gain was reduced,” Dr Ip said. “Without NPY, the weight gain on a high-fat diet with stress was the same as weight gain in the stress-free environment.
According to Professor Herzog, chronic high-insulin levels, driven by stress and a high-calorie diet, promote more and more eating. This creates a “vicious cycle” of overeating and weight gain.
“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,” Professor Herzog said.
While insulin imbalance is at the centre of a number of diseases, the study indicates that insulin has more widespread effects in the brain than previously thought.
“We were surprised that insulin had such a significant impact on the amygdala,” Professor Herzog continued. “It’s becoming more and more clear that insulin doesn’t only impact peripheral regions of the body, but that it regulates functions in the brain. We’re hoping to explore these effects further in future.”