Bengaluru/Mumbai, Sept. 27 -- Late in August, at Bengaluru's Koramangala, the city's familiar playground for startups and wellness brands, an unusual event was being planned. The invitation promised something that sounded like a weekend party, with music, food, networking and, intriguingly, "peptide tastings". Around 50 people were expected to attend.

The star of the evening was not supposed to be a cocktail or a new wellness product, but peptides, a class of compounds that has moved rapidly from the laboratory and pharmaceutical industry into the world of weight loss, muscle recovery, longevity and biohacking.

Soon as the "peptide party" was announced on X, it unleashed a wave of criticism from the medical fraternity, alarmed at what a...