When smokers quit using tobacco, a common and well known effect is increased appetite and weight gain. Smokers usually gain about 5-10 pounds after quitting, but there are some smokers that gain even more weight. For some people, this is a hindrance to quitting the unhealthy habit because they would rather smoke than to gain additional weight. Smokers have a noticeably lower body mass index as compared to non-smokers. Smoking as a method of weight control is well known. The exact mechanism whereby smoking influences weight, appetite, and weight gain is not well understood and remains unclear. In animal studies, nicotine in tobacco has been implicated as the compound responsible for the effects of smoking on food intake and body weight. In the past, little was known about the central nervous system pathways that are influenced by nicotine to control appetite, food intake, and weight gain. Researchers from Yale University School of Medicine and Baylor College of Medicine, lead by Dr. Marina Picciotto, have described experiments that identify the receptors, neurons, and central nervous system pathways used by nicotine to regulate weight. The study was published today June 10, 2011 in the journal Science. In experiments designed to identify antidepressants, the researchers noted that mice given nicotine, and a related compound cytisine, ate less, had more energy, and had less body weight. The researchers also showed that giving mice the noncompetitive nicotinic antagonist mecamylamine blocked the appetite suppressing effects of the nicotine. Nicotine is known to bind to and activate hypothalamic α3 β4 nicotinic acetylcholine receptors (nACHRs). When the researchers genetically knocked out the α3 β4 nicotinic acetylcholine receptors in mice the appetite suppressing effects of nicotine were lost. The researchers also identified that the α3 β4 nicotinic acetylcholine receptors were located on pro-opiomelanocortin (POMC) neurons in the hypothalamus of the brain. This finding is consistent with previously known roles for the hypothalamus in energy metabolism, appetite, food intake, and activity. This discovery suggests that drugs could be developed that bind to these receptors and could be used to help in smoking cessation and weight loss. The authors wrote that “Identifying these pathways could help to study potential cholinergic modulation of appetite and weight control and could also lead to the development of novel appetite suppressants that might aid in smoking cessation”. Dr. Nora D. Volkow, director of the National Institute on Drug Abuse, also commented that “These results indicate that medications that specifically target this pathway could alleviate nicotine withdrawal as well as reduce the risk of overeating during smoking cessation”. These findings are quite remarkable and future studies will focus on the development of medications that can help smokers quit the unhealthy habit and at the same time prevent them from gaining weight while doing so.
Why Smokers Eat Less
Yann S. Mineur et al. “Nicotine Decreases Food Intake Through Activation of POMC Neurons” Science 10 June 2011: Vol. 332 no. 6035 pp. 1330-1332 DOI: 10.1126/science.1201889