This thesis investigated how plate-clearing tendencies and food waste concerns may contribute to overconsumption from larger portion sizes of food. Chapter 2 demonstrated that, irrespective of the portion size served, those who self-reported a tendency to plate-clear when eating consumed significantly more food than those who reported low plate-clearing tendencies. Chapter 3 demonstrated the reliability and validity of a new scale to measure food waste concerns in an eating context. Scores on this scale positively predicted self-reported plate-clearing tendencies, but were not predictive of objectively measured energy intake, BMI or the likelihood of having overweight. Chapter 4 reports on studies in which beliefs about food waste were manipulated. Across Chapters 3 and 4, there was little evidence that food waste concerns influenced objectively measured food intake. Chapter 5 showed that plate-clearing tendencies and food waste concerns moderate the influence portion size has on intended food consumption. Given that intended consumption predicts actual consumption, individuals who are concerned about wasting food and habitually clear their plate may be at risk of overeating, especially when faced with larger portions. This thesis provides further evidence for a portion size effect on intended and actual consumption, with implications for policies and interventions aimed at reducing the size of portions available in our food environment. It also provides the first thorough investigation into how plate-clearing tendencies and food waste concerns influence food intake. My findings suggest that working to create a food environment in which plate-clearing would no longer constitute a maladaptive behaviour could induce widespread reductions in food intake. I also provide further evidence that food waste concerns are associated with plate-clearing tendencies. Further investigation into how food waste concerns influence plate-clearing tendencies, and how this may influence eating behaviour, is now warranted.