Dr. Peter Attia opens by critiquing conventional medicine's primary focus on treating disease after its onset, arguing for a more proactive approach specifically targeting extended 'healthspan' — years of genuine health and function, not merely extended lifespan alone.

Why this proactive-healthspan framing matters:

• Conventional medical practice often focuses primarily on treating conditions after they've developed, while Attia argues genuine longevity medicine should proactively address risk factors well before disease onset
• This distinction between mere lifespan extension and genuine healthspan — extended years of actual health and function — provides important reframing for the book's subsequent detailed guidance
• This opening establishes the book's foundational premise, motivating its subsequent detailed examination of specific proactive longevity strategies

This opening establishes the book's foundational premise, distinguishing proactive healthspan-focused medicine from conventional disease-treatment-focused approaches.