Caffeine is the world's most consumed psychoactive substance — and the most researched performance-enhancing compound in sports science. In this episode of Your Diet Sucks, Zoë Rom and Kylee Van Horn, RDN dig into how caffeine actually works, what the evidence says about endurance performance, sleep, hormones, and anxiety, and why both the wellness industry's fear-mongering and the pre-workout industry's escalation arms race are getting it wrong. From the history of coffee houses to the 1904 Olympic Marathon to dry scooping and adrenal fatigue myths — we cover it all.