Gorging on fatty comfort food really can make a stressed person feel better, scientific tests on unhappy rats have shown.
New research from the University of NSW found stressed animals were able to experience pleasure more easily if they ate high-fat foods.
The findings could explain whysome people over-eat when under stress, and it may even partially explain the obesity epidemic, said researcher Professor Margaret Morris.
"If it's true that societal levels of stress are increasing, and if people are turning to food in response to that stress, then it may be a small component of why we're experiencing more obesity," she said.
Professor Morris, who will deliver a lecture on the research in Sydney today, tested the theory by separating baby rats from their mothers soon after birth.
Tests using a sugar drink showed that these stressed rats were less able to sense pleasure than rats who hadn't been separated.
These unhappy rats were then placed on either a regular rat diet or an unhealthy Western diet with 30 per cent fat.
While the regular eaters maintain low-level pleasure - little interest in a sugary water offered to them - those on a fatty diet appeared happier, drinking as much of the substance as non-separated rats.
"It appears that the fatty diet almost counters the traumatic experience of the separation," Professor Morris said.
"This is a strong indication that having junk food available probably made them feel better, as seems to be the case in humans."
While the experiment was only in animals, Professor Morris said rodents were a reasonably good model of human response.
She said it was the strongest indication yet that early life stresses may have long-lasting impacts on the way we respond to stress, and whether we choose to eat in response to that stress.
The findings suggest that comfort eating is based on biology, rather than social behaviour.
They could also partially explain the rising trend in obesity in an increasingly stressful society.
"People are moving less, but changes in physical activity do not entirely explain why we're getting so much more obesity in our community," Professor Morris said.
"It's very likely that the link between stress and diet also plays a role."
