New research from UNSW on the effects of smoking has gone a long way to debunking one of the last justifications people use for continuing the habit - that is to keep them slim.

Professor Margaret Morris and Ms Hui Chen, from Pharmacology, School of Medical Sciences, found that any perceived loss of weight associated with smoking is most likely due to loss of lean body mass (muscle and internal organs) rather than loss of body fat.

Carried out in conjunction with the University of Melbourne, the study's findings were published this week in the American Journal of Physiology: Endocrinology and Metabolism.

The study found that even though tobacco-affected mice ate about 23 percent less, their fat levels were not significantly altered if they were consuming the high fat diet.

Further, in all animals that smoked, fat was deposited in the liver.

Professor Morris says the study shows that while smoking reduces appetite this is different from saying that cigarettes help to keep the body slim.

"If the findings can be applied to humans, and that's the first caveat, then this is very important research that shows that using smoking to suppress body weight gain is not going to be helpful," Professor Morris says.

"It is a very important health message that smoking does not lead to fat loss and continuing to smoke while eating a high fat diet is a very, very unhealthy thing to do."

Further collaborative work is examining the effects of smoking on muscle.

Media contact: Professor Margaret Morris, 9385 1560, Steve Offner, UNSW Media Office, 9385 1583 or 0424 580 208.