Back on the podcast, today is sleep, nutrition, and metabolism expert, Greg Potter, PhD. Through his academic research, public speaking, consulting and writing, Greg empowers people to make simple and sustainable lifestyle changes that add years to their lives and life to their years. His work has been featured in dozens of international media outlets, including Reuters, TIME, and The Washington Post, and he regularly contributes to popular websites, blogs, and podcasts. In this podcast, Greg is talking about light, including the importance of getting out in the sun and also modern problems with artificial light. He discusses the impact of light on the circadian system along with up-to-date recommendations related to light hygiene. We discuss practical tips for reducing light at night (not all of which involve putting away your device), and why not getting the right kind of light might be keeping you from achieving your body composition goals. Here’s the outline of this episode with Greg Potter:  [00:02:14] Wellics Corporate Wellness Software. [00:06:49] The importance of light. [00:08:30] The introduction of electric light. [00:09:55] myLuxRecorder (Satchin Panda's app, no longer available); Podcast: How to Use Time-Restricted Eating to Reverse Disease and Optimize Health, with Satchin Panda. [00:10:37] How light influences the circadian system. [00:15:34] Consensus paper with recommendations related to light hygiene; Study: Brown, Timothy M., et al. "Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults." PLoS biology 20.3 (2022): e3001571. [00:19:13] Practical tips for reducing light at night. [00:22:44] Increasing prevalence of myopia. [00:23:46] Podcast: Getting Stronger, with Todd Becker. [00:26:01] Vitamin D synthesis; Podcast: The Pleiotropic Effects of Sunlight, with Megan Hall. [00:26:15] Effects of light on mood and cognition. [00:27:24] Effect of light exposure patterns on cognitive performance; Study: Grant, Leilah K., et al. "Daytime exposure to short wavelength-enriched light improves cognitive performance in sleep-restricted college-aged adults." Frontiers in neurology (2021): 197. [00:28:14] Effects of light on metabolic health. [00:28:20] Dan Pardi podcast featuring Peter Light: Sunlight And Fat Metabolism: A New Discovery. [00:28:52] Effect of bright and dim light on metabolism (Netherlands); Study: Harmsen, Jan-Frieder, et al. "The influence of bright and dim light on substrate metabolism, energy expenditure and thermoregulation in insulin-resistant individuals depends on time of day." Diabetologia 65.4 (2022): 721-732. [00:30:53] Effects of light on skin and immune function. [00:31:57] Highlights #15 (topics: Sun avoidance & exposure, increasing testosterone, Robert Sapolsky). [00:35:14] Skyglow. [00:36:48] Light at night and endocrine disruption. [00:37:45] Light at night and quality/duration of sleep. [00:38:19] Blue light in the evening interferes with sleep homeostasis; Study: Cajochen, Christian, et al. "Evidence that homeostatic sleep regulation depends on ambient lighting conditions during wakefulness." Clocks & Sleep 1.4 (2019): 517-531. [00:38:53] Effects of light at night on sympathetic nervous system/cortisol; Study: Rahman, Shadab A., et al. "Characterizing the temporal dynamics of melatonin and cortisol changes in response to nocturnal light exposure." Scientific reports 9.1 (2019): 1-12. [00:39:26] Effects of light at night on heart rate, HRV, insulin resistance; Study: Mason, Ivy C., et al. "Light exposure during sleep impairs cardiometabolic function." Proceedings of the National Academy of Sciences 119.12 (2022): e2113290119. [00:41:34] Effects of moon phases on sleep; Study: Casiraghi, Leandro, et al. "Moonstruck sleep: Synchronization of human sleep with the moon cycle under field conditions." Science advances 7.5 (2021): eabe0465. [00:45:40] Effects of individual sensitivity to light; Study: Philli