Clearing one's plate out of habit when eating may promote excess energy consumption. This study examined whether plate clearing is related to increased body weight in a sample of young adults. It also sought to identify potential determinants of plate clearing. A cross-sectional design was used in which 385 young adults from a UK university completed self-report measures of plate clearing, weight and height, and demographic characteristics. Plate clearing was predictive of heavier body weight in both unadjusted and adjusted analyses. Parental encouragement to clear one's plate during childhood (retrospectively reported) and personal concerns about food waste were both independent predictors of plate clearing tendencies. Clearing one's plate when eating is associated with heavier body weight, and the prevalence of this behaviour may depend on parenting practices and concerns about food waste. Further work examining the longitudinal effect of plate clearing on weight gain is now needed.