In his new book, “Boundless: Upgrade Your Brain, Optimize Your Body & Defying Aging,” Ben Greenfield details his best longevity hacks. “Boundless” is a great title, as the object of longevity isn’t just about tacking on years of life, but finding ways to remain healthy and vibrant for as long as possible. In other words, it’s about quality and not just quantity of life.

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