In his mid-20s, Dave Asprey was a successful entrepreneur in Silicon Valley and a multimillionaire. However, he also weighed 140 kilograms, despite following his doctors' recommendations to eat only 1,800 calories six days a week and to exercise for 90 minutes. As his excess weight increasingly clouded his senses and cravings drained his energy and willpower, Asprey began to leverage the technologies that had made him wealthy to "hack" his own biology. He invested 15 years and $300,000 in various testing methods and self-experiments, from EEGs to a stay in a Tibetan monastery, to discover how to give his body and mind a maximum upgrade. He refers to this state as Bulletproof, which translates to "bulletproof" or "invulnerable" in German, describing the ability to consistently perform at peak levels.