What makes us tick? Our in-built clock – the circadian rhythm – plays a huge role in human longevity. Getting an appropriate amount of sleep while the sun is down has tremendous positive effects on our bodies, according to Dr. Felice Gersh, gynecologist and founder of the Integrative Medical Group of Irvine in Southern California. Sleeping in the dark keeps our body’s 24-hour internal clock on track and helps regulate our hormones and metabolism. Still, many people wind up staying up later than they planned, while others work night shift hours, which disrupts our internal clock. In this LLAMA podcast interview with Peter Bowes, Dr. Gersh describes what we can do to regulate our master clock when it is thrown off by lack of sleep or unconventional routines; why it matters for healthy aging and how our meal times could be the solution to night shift fatigue.