Do you head to the vending machine for an emergency snack as a work deadline approaches, or crave a sweet treat when your worries are piling up?

Stress is often accompanied by junk food cravings. And there is a scientific reason for this.

In a study on mice published in the journal Neuron, scientists from the Garvan Institute of Medical Research in Sydney found stress can create changes in the brain, leading to unhealthy habits and weight gain.

However, it is important to remember the issue is more complex in humans, and trying to restrict what we eat, particularly in stressful times, can be counterproductive.

Why do we eat when stressed?

Eating a delicious snack helps calm us down by triggering the brain’s reward system.

Professor Herbert Herzog is a visiting scientist at the Garvan Institute’s Eating Disorders lab and the study’s senior author.

He explains that in stressful situations, healthy food simply does not deliver the same reward boost that chips and lollies do.

“Because [junk food] is high in sugar, high in fat, and it’s easy to digest. So increasing your reward feeling might help you to cope with stress better,” Professor Herzog told ABC Radio Sydney.

Clinical psychologist Louise Adams from Untrapped Academy says seeking food that gives us pleasure in tricky times makes a lot of sense.

In a stressful situation, we’re more likely to let go of some of these self-imposed rules.

“We can more easily become disinhibited around food when we’re stressed because we’re kind of constantly white knuckling trying to be good around food,” Dr Adams says.

What does stress do to the brain?

Professor Herzog explains that our brain naturally regulates how much sugary and fatty foods we consume.

This is what’s called the anti-rewards system, or scientifically speaking, an area of the brain called the lateral habenula.

“So the brain tries to take your pleasure out of eating these kinds of [foods],” Professor Herzog says.

But they discovered that when the mice were stressed — by placing them in pairs and putting ice-cold water in their cage for an hour — this natural off-switch did not activate.

Professor Herzog believes a similar thing happens in humans as the neural pathways involved are very similar and a key molecule is identical.

What does this mean for human health?

Scientists are concerned that chronic stress will lead to eating increasing amounts of comfort food and gaining weight.

The stressed-out mice in the Garvan Institute’s study ate twice as much as their relaxed counterparts and their body weight increased twice as much.

In the mice, scientists intervened to block a molecule produced by stress, which led to mice eating less.

That’s not an option for humans though.

Professor Herzog’s advice is to try to reduce your stress levels as much as you can, which he admits is easier said than done.

No need to feel guilty about a ‘perfectly human’ response

Professor Herzog says it is important to be conscious of the amount and type of food you are eating when stressed.

“Ideally, you would stick to the fresh fruit section in the supermarket and avoid snack sections,” he says.

But Dr. Adams believes we need to rethink our relationship with food and stop feeling guilty.

“It’s important to emphasize it is perfectly human and understandable to do something that brings us pleasure when we’re in a stressful time,” she says.

“The thing is, if that’s immediately kind of judged, and we start feeling guilty about it, we actually start that whole restricting cycle again.”

She advocates for intuitive eating — tuning into your body’s needs and wants around food and enjoying everything you eat.

Even for the mice in the study, Dr. Adams reframes their behavior as a “triumph of evolution”.

Dr. Adams says the rodents’ weight gain is also “evolutionarily beneficial because their body’s helping store calories and energy so they can actually do something like plot and escape.”