Secret why stress makes you reach for the revealed chocolate

Scientists have discovered why we stress each — especially on foods like donuts, candy, and chocolate bars.

Australian researchers said when someone is full, part of the brain is activated to shut down reward signals from food, signaling them to stop eating.

But in experiments with stressed mice, the team found that this area remained quiet, prompting the rodents to continue eating for pleasure. Those in the stressed group gained twice as much weight as mice in the non-stressed group.

The scientists said their study highlights the importance of sticking to a healthy diet, especially when suffering from chronic stress.

Dr. Herbet Herzog, an eating disorder researcher at the Sydney-based Garvan Institute of Medical Research, said: ‘Our findings show that stress can override a natural brain response that diminishes the pleasure of eating – meaning the brain is continuously rewarded for eating.

‘We have shown that chronic stress, combined with a high-calorie diet, can lead to increased food intake and a preference for sweet, highly palatable foods, promoting weight gain and obesity.

‘This research shows how crucial a healthy diet is in times of stress.’

In the study, published today in the journal neuronscientists split mice into two groups and monitored how much food they consumed.

They were all offered the same high-fat diet for a short period of time and allowed to eat as much as they wanted.

One group of mice was kept under laboratory conditions, the other under chronic stress.

Scientists haven’t said how this was achieved, but previous cases involved hanging mice by their tails for an extended period of time until they stopped struggling. This is repeated to induce chronic stress.

Researchers found that the mice in the stressed group gained twice as much weight as the mice on the same diet that were not stressed.

Tests showed that a part of the brain known as the lateral habenula, which is located next to the thalamus, would remain silent when the mice were stressed.

In the non-stressed mice, this area turned on as soon as they were full, signaling that they should stop eating.

But for those who were chronically stressed, the area was not activated by satiety, prompting them to continue eating.

Scientists also conducted a “sucralose preference test” to solidify the results.

This was when the mice were presented with two options: drinking water or water that had been artificially sweetened.

They found that the stressed mice ingested three times more sucralose than those on a high-fat diet alone.

The researchers said that at the center of this response was a molecule called NPY, which the brain naturally produces in response to stress.

When researchers blocked NPY in stressed mice on a high-fat diet, the mice ate less comfort food and gained less weight.

Dr. Herzog added, “In stressful situations it’s easy to expend a lot of energy and the feeling of reward can calm you down.

“This is when an energy boost through food is helpful.

“But when stress is experienced over a long period of time, stress seems to change the equation, encouraging eating that is bad for the body in the long run.”

He added: ‘This research highlights how much stress can compromise healthy energy metabolism.

“It’s a reminder to avoid a stressful lifestyle, and crucially — if you’re dealing with long-term stress — try to eat healthy and lock in junk food.”

Scientists didn’t account for other factors that could also cause the stressed eating in mice, such as a disrupted sleep schedule.

It was unclear whether the results of these experiments in mice could be directly translated to humans.

Australia’s National Health and Medical Research Council funded the research.