Many people receiving treatment for addiction gain an excessive amount of weight during early recovery. We outline two hypothesized mechanisms that might explain weight gain: The Addiction Transfer Hypothesis, which suggests that some individuals respond to cravings with non-nutritive eating behavior, and the Propensity for Behavioral Addiction Hypothesis, which suggests that some people are at higher risk for addiction, and that excess weight gain results from a rebound of appetitive processes that were temporarily suppressed during active addiction.