Giving up smoking may lead to an average weight gain of about 5 kilograms (11 pounds) after 12 months, according to a review of 62 past studies.
That's higher than the 2.9 kilograms in weight gain often cited in smoking cessation advice leaflets, researchers at Universite Paris-Sud and the University of Birmingham in England said in the review published yesterday in the British Medical Journal. The finding was similar for both people who used nicotine replacement therapy and those who didn't, they said.
Nicotine, the addictive substance in cigarettes, quells appetite by latching onto certain brain receptors that crank up the activity of a system of neurons influencing food desire, according to a recent Yale University study. While most quitters in the reviewed studies gained weight, as many as 21 percent shed pounds and 14 percent gained more than 10 kilograms, indicating a wide variety of outcomes, the authors said.
"Some people are either destined or able to prevent weight gain without intervention, whereas others seem likely to gain enough weight that puts them at risk of diabetes, among other complications," the authors said in the published article. The varied effect on the bathroom scale "is rarely described or discussed in the literature" on quitting, they said.
Smoking is the leading cause of preventable death in the developed world and kills 443,000 and sickens 8.6 million each year in the U.S., according to the Centers for Disease Control and Prevention.
Gaining weight limits some of the health benefits of quitting and is associated with an increased risk of medical conditions such as diabetes, the authors said.
"These data suggest that doctors might usefully give patients a range of expected weight gain" and intervene early to keep quitters slim, they said.