Researchers at the University of Calgary's faculty of medicine think they have solved the riddle of why some people turn to food in stressful times.

Stress prompts nerve cells in the brain to transmit more urgent hunger signals — a process that probably dates back to humankind's earliest days, when finding food was a key source of stress.

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The hypothalamus regulates appetite and metabolism, as well as being a primary region of the brain responsible for the responses to stress. ((CBC))

The scientists at the Hotchkiss Brain Institute made the discovery by inducing stress in rats and observing their increased drive for food.

Published online this week in the journal Neuron, the discovery might provide important insight into why stress is thought to be one of the underlying contributors to over-eating and obesity, says Quentin Pittman, one of the researchers.

Normally the brain produces neurotransmitters — chemicals responsible for how cells communicate in the brain — called endocannabinoids.

These compounds, at work in the hypothalamus, send signals that regulate appetite and metabolism.

The hypothalamus is also the primary region responsible for the brain's response to stress.

Stress 'rewires' the brain

The Calgary researchers reported that when food was taken away from the rats, their ability to regulate food intake was impaired because a stress response occurred, temporarily causing "a functional rewiring in the brain."

This rewiring is thought to impair the endocannabinoids' ability to regulate food intake, resulting in an enhanced food drive.

"People who try to diet, for example, find it very difficult to maintain a low body weight because the nerve cells in our hypothalamus that control our appetite seem to switch on again and create a greater food drive," Pittman said.

But when the researchers blocked the effects of stress hormones in the brain, the absence of food no longer had this effect.

The next step is to find out whether other stressors affect rats in similar ways, Pittman said.