The DietCoach study aims to investigate the requirements of a digital dietary counseling platform, and evaluate the dietitian acceptance and usability of the DietCoach platform, which was developed based on the collected requirements. Additionally, the study examines how different levels of patient food purchase data availability affect these factors. The DietCoach platform automatically tracks historic and up-to-date patient food purchase data on loyalty cards and provides nutritional analysis, assisting dietitians in the dietary counseling process. The key research questions (RQ) are:

1. What are the requirements of a digital dietary counseling system based on food purchase data?
2. What is acceptance and usability of the DietCoach platform evaluated by dietitians?
3. How does the availability of patient food purchase data influence the acceptance and perceived usability of the DietCoach platform by dietitians?

Dietitians from several cantonal hospitals in the German-speaking area of Switzerland are invited to participate in the study. To answer RQ1, we conduct a workshop and a survey with dietitians to derive key requirements on dietary counseling systems. To answer RQ2 and RQ3, we use a cross-sectional, mixed-methods, between-subjects study design.

Researchers will evaluate and compare the acceptance and usability of DietCoach in 3 different conditions (3 patients that had different, i.e., high, medium and low, food purchase data availability). Each participant is assigned to the data of one patient. Participants are required to:

1. use the DietCoach platform to provide at least one dietary recommendation to patient food purchase data in two separate sessions.
2. provide quantitative and qualitative feedback about the acceptance and usability of the DietCoach platform.

The DietCoach study aims to investigate the requirements of a digital dietary counseling platform, and evaluate the dietitian acceptance and usability of the DietCoach platform, which was developed based on the collected requirements. Additionally, the study examines how different levels of patient food purchase data availability affect these factors. The DietCoach platform automatically tracks historic and up-to-date patient food purchases on loyalty cards and provides nutritional analysis.

Dietitians from several cantonal hospitals in the German-speaking area of Switzerland are invited to participate. To collect the key requirements of a digital dietary counseling platform based on food purchase data, we conduct a workshop and a survey, using guiding questions designed based on our research over the last years. To understand the acceptance and usability of DietCoach and how food purchase data availability influences these factors, we use a cross-sectional, mixed-methods, between-subjects study design. Each participant is assigned to the data of one patient. Participants need to:

1. use the DietCoach platform to provide at least one dietary recommendation to patient food purchase data in two separate sessions.
2. provide quantitative and qualitative feedback about the acceptance and usability of the DietCoach platform.

The DietCoach usability study includes three conditions (data from three patients), defined by High, Medium, and Low levels of patient food purchase data availability. Data availability is determined by the number of baskets/items (from the major Swiss retail chain) per person in a patient household. Participants are randomly assigned to the data of one patient.

In both the initial and follow-up sessions, participants need to provide at least one dietary recommendation based on the patient's health status and food purchase data over 8 weeks. The food purchase data in the follow-up session covers the 8 weeks immediately following those considered in the initial session. After completing the assigned tasks on the platform, participants are asked to complete a survey assessing their acceptance of and the usability of the DietCoach platform.

Inclusion Criteria:

• Dietitians in Switzerland
• German-speaking (the platform is in German, a main language in Switzerland)

The study aims to include all dietitians in Switzerland as potential participants. However, since recruitment will be conducted through contacting the nutritional departments of cantonal hospitals in the German-speaking area, the participant pool is expected to consist primarily of dietitians from several cantonal hospitals located in the German-speaking region of Switzerland.

We plan to publish anonymized partial food purchase data of the selected patients, and the corresponding dietary recommendations from the DietCoach study participants (dietitians)

1. The data will be published in an anonymized form.
2. Only purchase records that can be identified by our food composition database and belong to relevant food categories will be published.

The data will become available in 2024/2025, published as supplementary materials to the corresponding paper to ensure the result reproducibility. It will be available until participants request to delete their data. Published aggregated results could not be withdrawn retrospectively.