Stress just as unhealthy as junk food

"We sometimes think of stress as a purely psychological phenomenon, but it causes distinct physical changes," said Laura Bridgewater, Professor at Brigham Young University in Utah, US. 

The study, published in the journal Nature Scientific Reports, found that when female mice were exposed to stress, their gut microbiota -- the microorganisms vital to digestive and metabolic health -- changed to look like the mice that had been eating a high-fat diet.

Bridgewater and her collaborators at Shanghai Jiao Tong University in China took a large group of eight-week-old mice and exposed half of the males and half of the females to a high-fat diet. 

After 16 weeks, all of the mice were exposed to mild stress over the course of 18 days.

Researchers then extracted microbial DNA from the mice fecal pellets before and after the stress to test how the gut microbiota was affected. 

They also measured mouse anxiety based on how much and where the mice travelled in an open field arena.

The researchers found fascinating differences between genders: Male mice on the high-fat diet exhibited more anxiety than females on the high-fat diet, and high-fat males also showed decreased activity in response to stress. 

However, it was only in female mice that stress caused the gut microbiota composition to shift as if the animals were on a high-fat diet.

While the study was only carried out on animals, the researchers believe there could be significant implications for humans.

"In society, women tend to have higher rates of depression and anxiety, which are linked to stress" said Bridgewater.

"This study suggests that a possible source of the gender discrepancy may be the different ways gut microbiota responds to stress in males vs. females," Bridgewater added.