Valter Longo, PhD, author of The Longevity Diet, sat down with Elise Loehnen at In goop Health to share what he’s learned about our ability to optimize our health largely through diet and lifestyle changes. Longo, who is the director of the USC Longevity Institute, continues to conduct a wide range of fascinating research on different forms of fasting: What kind of fast is safest? How does fasting affect the body? Could particular forms of fasting have beneficial outcomes for particular health concerns? (Some of this research contributed to the development of ProLon, a five-day fasting-mimicking meal kit that is growing in popularity, in part because you actually eat during the program.) Beyond fasting, Longo explains what he believes to be the best way to eat (and when) based on the research.