Introduction Obesity prevalence has increased globally, imposing a significant burden on individuals and societies. Innovative solutions are, therefore, essential to mitigate its impact. Methods and analysis This protocol outlines the framework of seven independent European pilot studies conducted in Bulgaria, Germany, Luxembourg and Spain, under the EU-Horizon HealthyW8 project. These studies aim to evaluate as primary outcomes feasibility, usage patterns (adherence) and user satisfaction of the Healthy Lifestyle Recommender System (HLRS), a personalised digital tool designed to promote healthy lifestyles through tailored physical activity and meal recommendations, considering emotional aspects. The seven pilot trials will collectively include 240 (around 30 participants/trial) older adults (>= 65 years) with overweight (body mass index (BMI) 25.0-29.9 kg/m2) over a 3-month period. As a recruitment mitigation strategy, we will extend the age range to include individuals aged >= 55 years and those with normal weight (BMI 18.5-24.9 kg/m2). Other parameters collected include anthropometric measurements, questionnaires to survey lifestyle (alcohol and tobacco consumption, sleep quality), dietary patterns (food frequency questionnaire and 24-hour recall) and emotional well-being, as well as data collected from wearable devices (smartwatch, accelerometer) to track 24-hour activity patterns. Additionally, two pilot studies will collect blood, urine, saliva (only one partner) and stool samples to explore biomarkers of inflammation, oxidative stress, gut microbiome and circulating miRNAs. Expected outcomes It is hypothesised that participants will use the HLRS consistently enough to assess its feasibility and impact. The findings will contribute to planning and executing long-term trials focused on health outcomes and enhance understanding of the multimodal nature of obesity risk and its comorbidities. This protocol facilitates comparisons across studies in diverse cultural and contextual settings, offering insights into how personal and environmental factors influence the implementation and effectiveness of the HLRS. Ethics and dissemination Ethical approval has been obtained in each country independently. Dissemination efforts will prioritise high-impact journal publications.Trial registration number NCT07011368.