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Researchers from UNSW and the University of Melbourne have found that smoking reprograms the brain's responses to hunger signals.

"Gaining weight after quitting is one of the main reasons men and women start smoking again," said UNSW Professor of Pharmacology, Margaret Morris, one of the authors of the report. "But until now, we didn't know exactly how the two were connected."

The paper, which has just been published in the high-impact American Journal of Respiratory Critical Care Medicine, has found that one of the main regulators of appetite, called neuropeptide Y (NPY), which works directly on the brain's appetite centre is affected by smoking.

"The changes, which occur in the brain's hypothalamus, control some of our strongest behaviours, which may be one of the reasons smoking is so hard to give up," she said.

"This finding could have a two-fold health benefit, by helping people stop smoking and preventing weight gain," Associate Professor Gary Anderson of the University of Melbourne said. "The results could also help to explain part of the serious wasting syndrome that chronic smokers suffer from."

The researchers found that mice exposed to long-term cigarette smoke had a lower food intake and smaller body and fat mass compared to animals without exposure.

Brain levels of the appetite stimulant NPY were decreased in the animals exposed to cigarette smoke. In animals not exposed to smoke, but with a similar reduction in food intake, NPY was unchanged.

The work is a collaboration between the Department of Pharmacology and the CRC for Chronic Inflammatory Diseases, both at the University of Melbourne, in conjunction with UNSW.

The research was funded by the National Health and Medical Research Council of Australia and the CRC for Chronic Inflammatory Diseases.

The other authors of "Cigarette smoke exposure reprograms the hypothalamic neuropeptide Y axis to promote weight loss" are Hui Chen, Michelle Hansen, Jessica Jones, Ross Vlahos and Steve Bozinovski.