How can we promote the health of people aged 40–55? Adopting a life-course approach—as recommended by the World Health Organization (WHO)—broadens the scope of prevention and health promotion to all stages of life within a continuum framework. In the French context, this spans from the first 1,000 days to “aging well,” with the goal of improving health for all citizens. This approach pays particular attention to the different stages of life, including phases of development, transition, and vulnerability. It takes into account the living conditions and environments that can vary throughout the life cycle (the importance of the school environment, the workplace, etc.) and present opportunities for health-promoting behaviors and living and social environments.