Among a host of physiological and psychological factors that contribute to the maintenance of smoking behavior, using smoking as a regulation strategy in order to reduce negative affect figures prominently (Tate & Stanton, 1990; Tomkins, 1966; Torres & O’Dell, 2016). For example, smokers report that stress motivates them to smoke and stress-induced smoking has also been demonstrated experimentally (Kassel, Stroud, & Paronis, 2003; Marks, Murray, Evans, & Vida Estacio, 2011). Eating is another way for many individuals to cope with stress (Greeno & Wing, 1994). In contrast to smoking, which is increased by stress, however, stress may increase food intake in some individuals, but can also lead to reduced food intake in others (Oliver & Wardle, 1999). Smoking appears to be a primary reinforcer while reinforcing properties of natural rewards such as food are reduced in current smokers. For example, current smokers had reduced activation of reward-related brain areas in response to food cues (Jastreboff et al., 2015) and—in contrast to nonsmokers—showed an approach bias towards smoking-related cues but not towards food cues (Machulska, Zlomuzica, Adolph, Rinck, & Margraf, 2015). In line with these findings, current smokers tend to have a lower body mass index (BMI) than nonsmokers, which may be due to both nicotine-induced increases in energy expenditure and decreases in appetite (Chiolero, Faeh, Paccaud, & Cornuz, 2008). In this study, relationships between smoking status, stress, stress eating, and BMI were examined. Based on the above-mentioned findings, it was expected that current smokers would have a lower BMI than nonsmokers. Furthermore, current smokers were expected to report a tendency to eat less when stressed, due to their preference for smoking in response to stress. In addition, if such a mutual exclusiveness of either smoking or eating in response to stress represents a central mechanism of reduced BMI in smokers, then this stress-induced reduction in food intake would mediate the effect of smoking status on BMI. Finally, it was expected that these effects would be particularly pronounced in individuals who actually report experiencing high levels of stress and, thus, that perceived stress would moderate the indirect effect of smoking status on BMI. Therefore, a moderated mediation model was proposed, in which being a smoker was associated with a lower BMI through less stress eating, particularly in stressed individuals (Figure 1).