Effects of smoking status and smoking cessation on leptin levels.

Cigarette smoking is associated with lower body weight, and quitting smoking typically produces weight gain. An effect of chronic smoking on increasing leptin, a protein product associated with reducing weight, may help explain this influence of smoking on lowering body weight. We examined fasting serum leptin levels in male and female adult smokers (n = 52) and non-smokers (n = 12) as well as long-time ex-smokers (n = 13), with all groups similar in body mass index (BMI). Partial regression analyses controlling for BMI and, where relevant, age were used to relate leptin to indices of smoking exposure and dependence within the smokers, and with typical alcohol and caffeine intake in the entire sample. Furthermore, a subset of the smokers (n = 22) quit for at least 3 weeks, and changes in leptin and weight were prospectively assessed. Results showed no difference in mean leptin levels as a function of smoking status and no significant associations of leptin with smoking exposure variables after controlling for BMI and age. However, leptin was significantly correlated with alcohol intake (inversely) in women. In addition, smoking cessation increased leptin, the opposite change expected if leptin were responsible for weight gain, but again only in women and not in men. This leptin change remained significant after controlling for the increase in weight observed in both men and women. In conclusion, the influence of cigarette smoking on body weight does not appear to be due directly to changes in leptin levels, as there is no difference in leptin due to smoking status and leptin does not decline after cessation.