Quit smoking and chances are you'll gain weight -- five kilograms in the first year, to be precise.
New research pinpoints exactly how the weight gain starts -- and also shows the key to avoiding quitter's weight gain.
In the study, a group of smokers were separated into two groups. One group had to quit smoking for a night while the other could have two cigarettes.
The next day, both groups were presented with unlimited snacks and researchers observed the smokers ate 152 fewer calories than those abstaining and felt just as full and satisfied.
The study, presented at the European Respiratory Society International Congress, put the appetite suppression down to a hormone called ghrelin, nicknamed the 'hunger hormone'.
Researchers tested the participants for presence of ghrelin, which makes you feel full, and found ghrelin concentration was lower among non smokers for 60 minutes after eating.
Harokopio University Athens researcher Konstantina Zachari said ghrelin could be the key to avoiding quitter's weight gain.
"In our small study, we found that smoking had an acute effect on energy intake that could be mediated by alterations in ghrelin levels," Zachari said.
If you put on weight after quitting
Don't despair. A few extra kilograms are a much lower risk compared to the risk of continuing to smoke.
You would have to gain more than 40 kilograms above your recommended weight to equal the risk of heart disease posed by smoking.
Be kind to yourself if you do put on a few kilos. You are boosting your health by quitting.
Try increasing strength-based exercise because muscle tissue burns more kilojoules than fat.
Eating more fruit, vegetables and whole grains can also make you feel fuller.
"Further research is needed to investigate whether these results would be duplicated in a broader study population.
"We also need to investigate other potential biological mediators and ways to balance post-cessation weight gain in order to achieve higher smoking cessation rates and lower relapse rates."