Health advisers begin meeting Thursday to review more than a half-dozen peptides, unproven substances that have become a growing wellness trend despite little evidence they are safe or effective.

The two-day meeting hosted by the Food and Drug Administration has the backing of Health Secretary Robert F. Kennedy Jr., who has described himself as a “big fan” of peptides and vowed to overturn industry restrictions put in place under President Joe Biden.

Peptide supporters include podcaster Joe Rogan and wellness influencers such as Gary Brecka, a supporter of Kennedy’s “Make America Healthy Again” agenda who sells peptide vials online. Social media platforms are brimming with testimonials from people claiming the substances helped them build muscle, recover from injuries or look younger.

Despite such support, the FDA’s two-day meeting is expected to showcase a stark split over the compounds.

FDA’s career scientists have made clear they don’t think there’s enough data to support making peptides more widely available, specifically from compounding pharmacies, which mix customized medicines that aren’t available from traditional drugmakers.