Sellers promote unlicensed weight-loss drugs through giveaways on WhatsApp and Telegram.
They offer injectable medicines as prizes in time-limited competitions.
The Guardian found groups advertising retatrutide, an unapproved experimental drug.
Experts warn these promotions pose serious health risks.
One group offered retatrutide, Glow pens, and melanotan II as a prize bundle.
None of these injectable products hold UK approval.
UK law restricts weight-loss injections to prescription-only supply.
Unapproved drugs cannot be legally sold or advertised.
Some sellers disguise drug sales as fitness coaching programmes.
Platforms say they ban illegal drug sales and remove such content.
