When science journalist Bas Kast collapsed at the age of 40 with chest pains, he faced an existential question: Had he ruined his health with junk food? He resolved to radically change his diet to heal himself. But what is truly healthy? This marked the beginning of a multi-year journey into current aging and nutrition research. What do particularly long-lived populations eat? How can one lose weight efficiently? Can typical age-related ailments be avoided? Is it possible to "eat young" with certain foods? Much of what we consider healthy eating can actually be harmful. From thousands of sometimes contradictory studies, Bas Kast filters out the scientifically validated insights about what constitutes a truly healthy diet.