Australian scientists have confirmed what many chocoholics already know, that “comfort food” can reduce stress.

Eating foods rich in fat and sugar can alter the chemical composition of the brain and reduce anxiety, says Professor of Pharmacology Margaret Morris.

Prof Morris, from the University of NSW’s School of Medical Sciences, conducted a study of rats which showed the effects of past trauma could be erased through “unlimited access to yummy food”.

“Implementing that diet reversed their anxiety … it took an animal back to the non-stressed state,” Prof Morris told AAP.

“We really don’t know why that happens, but there seems to be a biochemical link.”

The research started with different groups of baby rats – one group grew up with normal contact with their mothers, while the other group had lengthy periods of separation.

Rats with a more traumatic early life were found to have higher levels of stress hormones and fewer steroid receptors in the part of the brain which controls behavior.

The signals for “anxiety and depression” eventually disappeared among those rats who were later switched to the all-you-can-eat junk food diet.

“The control group had no effect from the diet really, but the stressed animals had a deficit … which was restored by the diet.”

“(The) food seems to affect neurogenesis similar to the way anti-depressants promote nerve growth in the brain.”

Prof Morris cautioned while the results were not immediately transferable to people, it did show support “the therapeutic value of comfort food” and hint at explanations for other patterns of human behavior.

“If you ask people what they eat when they are stressed, they eat more chocolate, cakes and sweets, and less fish, vegetables and fruit,” she said.

And: “There is good evidence that if we look at people who have experienced trauma as a child tend to be heavier as adults”.

The study also should not be seen as an endorsement of eating junk food, Prof Morris said, noting this would set people on a path to other serious health problems.

Future research would aim to determine whether other rewarding activities – such as exercise – could have a similar stress-busting affect on rats’ brains.

The research was conducted jointly with PHD student Jayanthi Maniam, and it is published in the journal Psychoneuroendrocrinology.