Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Horizon 2020 Research and Innovation project. Background Appropriate nutrition and physical activity (PA) are essential for the management of a large number of non-communicable diseases. Nonetheless, our lifestyle is characterized by an irregular and often poorly balanced dietary pattern and insufficient PA. Purpose The digital health application PROTEIN, which was developed within the framework of H2020 Research and Innovation project PROTEIN, aims to engage people in a healthy, nutritionally sound and active life. To obtain information on the acceptability, usability, and feasibility as well as preliminary effectiveness, pilot trials are being conducted in various countries. Results from these pilots aim to guide the further development of personalized nutrition applications. Methods A prospective pilot study was implemented between May-October 2022. Participant attitudes and beliefs about their diet and PA were assessed by means of the readiness to change questionnaire. Their habits, including smoking, diet (MEDAS), alcohol consumption, (AUDIT) and PA (IPAQ) were evaluated at baseline and follow-up. The usability and feasibility were evaluated by the System Usability (SUS) and User Experience Questionnaire (UEQ). A general profile of the participants was assessed, as well as their attitudes and beliefs around their lifestyle. Results Fifty participants were included (women, n=30), 27 of them being overweight or diagnosed with obesity and 23 patients with CVD. On average, age was 49.9 years (19-76) and BMI was 32.3 (16.7–45.3). 40.4% of the participants believed they were PA enough, 42.9% thought they were not. 74% were motivated to become more active. Almost half of the patients (47.6%) were convinced already enjoying a healthy diet, 33.3% were not sure and 19.1% reported they were not. The majority (81%) were motivated to eat healthier. Results from MEDAS show an increase in the intake of vegetables, fruit, legumes and nuts. A decrease was observed in the consumption of meat, butter and candy. (Table 1) 70% reported being highly active at baseline, 21% and 9% reported being medium and low active respectively. Of the patients filling in all the questionnaires (n=25), 20% reported an increase in PA, 70% maintained their PA level and 8% reported a decrease. Results from the SUS showed that most of the participants found the app orderly (64%), attractive (63%) and congenial (76%). However, participants reported to find the app unnecessarily complex (60%), counterintuitive (48%) or cumbersome (68%). Conclusion Participants were motivated to change their lifestyle towards a healthier one. Despite this, a drop-out rate of 41.8% was observed. Users that completed the intervention experienced a positive effect on the maintenance or progress of their PA or diet-behaviour. Currently, it seems that the PROTEIN application is too complex to be user-friendly. There is need to adjust the functionality of the app according to the feedback from users to ensure an optimal impact on their lifestyles.