Healthy and sustainable diet and physical activity: the rationale for and experiences from developing a combined summary score.

Aims: First, to describe the rationale for developing a combined summary score, the Healthy and Sustainable Dietary and Physical Activity habits (HSDPA) score, incorporating four selected dietary and physical activity aspects: (a) the New Nordic Diet, (b) local and sustainable foods, (c) active transportation and (d) non-exercise outdoor activities. Secondly, to describe the experiences from constructing the HSDPA score. Methods: Relevant literature covering the four aspects of interest was reviewed to secure a well-grounded rationale and a theory-based approach. To measure compliance with such a broad approach targeting diet, physical activity, health and environmental sustainability, the HSDPA score was constructed including one subscale for each aspect. The four subscales were constructed from questionnaire items and were equally weighted, entailing a range from 0-10 points, hence the total HSDPA score ranged from 0-40 points. Results: In retrospect, we believe that the rationale for creating the HSDPA score is reasonable. Still, emphasizing fewer, but the most relevant aspects, such as reduced meat consumption and active transportation, may represent a more functional solution than the broad approach suggested herein, both for promoting public health and environmental sustainability, and for developing a feasible measurement tool. Conclusions: Our experiences illustrate the importance of methodological perspectives and scrutiny related to both the development and testing of complex summary scores. Nevertheless, we think that combined summary scores could be applicable for use within epidemiological studies and for measuring the effects of interventions, if accounting for the methodological limitations as far as possible.