In Chapter 10, Attia emphasizes how our modern life has extended lifespan but “also created conditions that conspire to limit our longevity in certain ways” (210). Our modern environment has changed drastically from the environment in which the human species evolved, yet, our genes have barely changed (See: Background). Humans must work hard if we are going to adapt to this new environment and “live longer, and live better for longer” (40).

Chapter 10 outlines the rest of the book. Whereas Part 2 focuses on understanding what predisposes us to the Horsemen diseases and how they progress, Part 3 examines the tactics we can use to navigate this new environment and achieve longevity. Attia focuses on four of the five tactical domains that people can address to alter their healthspan and lifespan: exercise (Chapters 11-13), nutritional biochemistry (Chapters 14-15), sleep (Chapter 16), and emotional health (Chapter 17). Exogenous molecules, including drugs, hormones, and supplements, represent the fifth domain, which Attia touches on in Part 2 (e.