Hidden-market sellers promote unlicensed weight-loss drugs through WhatsApp and Telegram giveaways.
They offer injectable medicines such as retatrutide as competition prizes.
The Guardian found groups using countdowns and peer sharing to pressure users.
Experts warn these tactics pose serious health risks.
None of the promoted drugs hold UK approval.
Law allows weight-loss injections only with prescriptions from licensed providers.
Some sellers disguise drug sales as fitness or coaching programmes.
Researchers say these practices trivialise medical risks and bypass safeguards.
