Metabolic syndrome (MetS) refers to the co-occurrence of health conditions that increase the risk of cardiovascular disease, stroke and type 2 diabetes. It disproportionately affects low socioeconomic (SEP) populations, and traditional healthcare often fails to support lasting lifestyle changes. While eHealth interventions are promising many lack personalization for high-risk, low-SEP groups. To bridge this gap, we developed the HealthBox, a tailored eHealth tool combining tele monitoring and digital coaching to promote healthier habits and reduce chronic disease risk. A key step was understanding user diversity to guide personalization strategies. In this first-phase study, we conducted semi- structured interviews with nine MetS patients, identifying personalization determinants across three categories: personal and health factors, behavioral tendencies, and system-related aspects. These insights highlight user variability in managing MetS and engaging with eHealth, forming a foundation for future personalized interventions.