What we eat and drink is the most important predictor of obesity, and health more broadly. Accurate information on food and drink consumption is critical to identifying the categories of food, and more specifically the ingredients, that are contributing most to daily calorie intakes in Wales. This would enable us to target interventions much more effectively.

However, accurately tracking dietary data presents several challenges including a tendency for individuals to underreport their consumption in dietary surveys. For this reason, we explore the availability of purchase data, which has been used as a proxy for consumption. However, purchase data is typically only available through commercial providers where costs can be prohibitive. Moreover, purchase data has its own limitations such as not knowing how much of the food purchased is actually consumed or by who in a household. Since consumption data is already collected — albeit with relatively small samples of Welsh participants — boosting sample sizes of these surveys, particularly the National Diet and Nutrition Survey, could deliver significant value.