[Relationship between smoking status and obesity risk in males aged 18-64 years in 9 provinces of China, 1991-2015]

Objective: To investigate longitudinal association between smoking behavior and obesity risk in male adults in China from 1991 to 2015. Methods: A total of 32 169 male adults aged 18-64 years who participated in two or more rounds of China Health and Nutrition Survey (CHNS, 1991-2015) and had complete information of demographic characteristics, smoking status and physical measurements were selected as the study subjects. According to whether the subjects smoked or not and the number of cigarettes smoked per day, the subjects were divided into four groups: nonsmoker, light smoker (1-14 cigarettes/d), moderate smoker (15-24 cigarettes/d) and heavy smoker (≥25 cigarettes/d). The distribution of body mass index (BMI), waist circumference (WC), general obesity and central obesity of subjects with different smoking status were observed. Two-level mixed effect linear regression model and logistic regression model were used to analyze the relationship between smoking status and obesity risk. Results: Compared with nonsmokers, the BMI decreased by 0.19 kg/m² in light smokers (95%CI:-0.27--0.10), 0.40 kg/m² in moderate smokers (95%CI:-0.49--0.31), and 0.36 kg/m² in heavy smokers (95%CI:-0.53--0.19), respectively, and the WC decreased by 0.49 cm in light smokers (95%CI:-0.76--0.21), 0.80 cm in moderate smokers (95%CI:-1.08--0.51) and 0.79 cm in heavy smokers (95%CI:-1.38--0.36) in, respectively. Compared with nonsmokers, the odds ratio of the risk for general and abdominal obesity were 0.70 (95%CI:0.62-0.79) and 0.78 (95%CI:0.73-0.84) in light smokers, 0.61 (95%CI:0.55-0.69) and 0.74 (95%CI:0.70-0.79) in moderate smokers and 0.78 (95%CI:0.65-0.96) and 0.84 (95%CI:0.76-0.95) in heavy smokers, respectively. Conclusions: From 1991 to 2015, the BMI, WC, prevalence of general and abdominal obesity in male adults showed a significant upward trends in both nonsmokers and smokers (light, moderate and heavy) in China, suggesting that smoking is negatively associated with the risk for obesity in male adults.