The Diet-related GHG Index: construction and validation of a brief questionnaire-based index

The aim was to construct and validate a cost-efficient index to measure GHG emissions (GHGe) caused by Danish consumers’ diets to be employed in questionnaire-based surveys. The index was modelled on the basis of actual food purchase data from a panel of ordinary Danish households and a questionnaire consisting of food frequency questions issued to the same panel. Based on the purchase data, diet-related GHGe were calculated for 2012. The data was then split into a learning sample and a validation sample. The index was constructed using the learning sample where a scoring procedure was calculated from responses to the questionnaire-based food frequency questions that predicted diet-related GHGe. Subsequently, the index scoring procedure was employed on the validation sample and the empirical relevance of the index was examined. In the learning sample, a scoring procedure to construct the index was developed on basis of 13 food frequency questions. In the validation sample, the index accounted for considerable variation in diet-related GHGe. Furthermore, the index was associated with the same socio-demographic and attitudinal factors as identified with calculated diet-related GHGe using food purchase data. Surprisingly, in this analysis, people’s sense of obligation to do something about global warming did not lead to decreased GHGe. Higher social status and gastronomic interest, meanwhile, led to increased GHGe. The index can be used in future questionnaire surveys as a cost-efficient way to estimate diet-related GHG emissions of Danish consumers. Since the index is responsive to relevant socio-demographic and attitudinal factors, it can be utilised to monitor key attitudinal/habitual and socio-demographic drivers of change.