As a fitness editor in New York City, I first started picking up chatter about peptides around 2016. Longevity was just being written into the wellness lexicon and things like NAD, red light therapy, and cold plunging were taking their first steps into the mainstream. But peptides were an outlier. For one, you had to inject them, which seemed sketchy. More important, there was virtually no research to back up their efficacy. On top of that, they were expensive. So peptides hung back on the fringes, quietly gaining traction among what would soon emerge as the inaugural class of biohackers. That all changed with the introduction of weight-loss drugs like semaglutide, tirzepatide, and, most recently, retatrutide—all peptides. The meteoric rise in popularity of drugs like Mounjaro and Zepbound has in short order stripped much of the doubt and stigma surrounding peptides, including the requisite self-inflicted needle jabs. Meanwhile, as the biohacking crowd has grown increasingly larger—and louder—having infiltrated popular culture through every major entrypoint from Netflix to the podcastsphere, anecdotal accounts of peptides’ benefits have …