Conclusion
This novel image-based tool developed to estimate perceived portion size norms of discretionary foods showed good agreement with real foods. This tool may be valuable for investigating perceived portion size norms of common discretionary foods in a variety of eating contexts. A better understanding of current portion size norms could be used to inform the development of public health messages and food labelling. It can also help guide the food industry to provide serving sizes more aligned with consumers’ norms and nudge towards smaller sizes over time. This could help create food environments that encourage consumers to select more appropriate discretionary food portion sizes to prevent the overconsumption of these foods.