This paper introduces PLOS (Preventive Lifestyle Operating System), an AI-driven framework designed to shift healthcare from reactive treatment to continuous, personalised prevention. The system integrates multi-dimensional health data, including sleep, nutrition, physical activity, stress, and biomarkers, into a unified intelligence layer. Through predictive modelling, risk scoring, and adaptive learning, PLOS enables early detection of health risks and delivers personalised lifestyle and nutraceutical interventions. The framework operates through a continuous feedback loop, allowing dynamic optimisation of health outcomes over time. PLOS aims to provide a scalable architecture for preventive healthcare across individuals, enterprises, and broader health ecosystems.