Never-smokers with a positive family smoking history are more likely to be overweight or obese than never-smokers with a negative family smoking history.

To shed light on the complex relationship between smoking and body weight, we used never-smokers stratified on family smoking history to model the effects of a diathesis for smoking on body weight without the potential confound of metabolic changes or decreased physical activity caused by chronic tobacco smoke exposure. Participants were 100 family history negative never-smokers (FH-; 2 never-smoking parents) and 71 family history positive never-smokers (FH+; 2 ever-smoking parents). Controlling for significant group differences in race and age, BMI was significantly higher in FH+ (26.7+/-.6) than in FH- (24.5+/-.4; F=10.351 p<.01). Further analysis using logistic regression showed that FH+ were 2.7 times as likely to be overweight/obese (BMI > or = 25; 95% C.I. 1.398-5.351; p<.01). FH+ scored significantly higher on the Dieting and Bingeing Severity Scale than FH- and were significantly more likely to score in the severe or at-risk range. FH+ drank significantly more alcohol than FH-; they scored significantly higher on the CAGE and on the Michigan Alcohol Screening Test. Our analyses provide support for the role of inherited and/or environmentally-driven tendencies towards disinhibited eating and/or risky behaviors in general in the observed differences in BMI. No group differences in BMI or likelihood of being overweight/obese emerged based on prenatal exposure to nicotine in FH+ smokers, although our sample was too small to rule out an association. Further research in larger samples, using more complex statistical models, will be needed to disentangle these issues and identify causal pathways.