Reciprocal relations between weight and psychological factors suggest that there are deep connections between mind and body. Personality traits are linked to weight gain; weight gain may likewise be associated with personality change. Using data from two diverse longitudinal samples (N = 1,919) collected at two time points an average of 10 years apart, we showed that significant weight gain is associated with increases in both impulsiveness and deliberation: In both samples, middle-aged adults who gained 10% or more of their baseline body weight by follow-up increased in their tendency to give in to temptation, yet were more thoughtful about the consequences of their actions. The present research moves beyond life events to implicate health status in adult personality development. The findings also suggest that interventions focusing on the emotional component of impulse control may be more effective because even people who become more thoughtful about the consequences of their actions may have limited success at inhibiting their behavior. © The Author(s) 2013.