Toronto, Aug 14 (IANS): Scientists have figured out why stress triggers appetite, which could be instrumental in causing obesity.

Normally, the brain produces neurotransmitters (chemicals facilitating intercellular communication) called endocannabinoids that send signals to control appetite.

Hotchkiss Brain Institute (HBI) researchers at the University of Calgary found that in the absence of food, a stress response temporarily causes brain re-wiring.

This re-wiring may impair the endocannabinoids' ability to regulate food intake and contribute to increased food drive, the journal Neuron reports.

By blocking the effects of stress hormones in the brain, researchers caused the brain wiring to remain unchanged in food's absence, according to a Calgary statement.

Hotchkiss researchers Jaideep Bains and Quentin Pittman, looked specifically at nerve cells (neurons) in hypothalamus. This brain structure plays a key role in controlling appetite and metabolism and also linked with the brain's response to stress.

Bains, who based his study on rats, explains: "Interestingly, these changes are driven not necessarily by the lack of nutrients, but rather by the stress induced by the lack of food."

"The absence of food clearly brings about dramatic changes in the way our neurons communicate with each other. . . . The fact that the lack of food causes activation of the stress response might help explain the relationship between stress and obesity," adds Pittman.