Leaflets which claimed foot pads could help the wearer lose weight by sucking out excess fat have been pulled.
Around 30,000 people may have responded to the "Lipo-Slim" mailings sent by a Lebanese company, the Office of Fair Trading said.
The mailings claimed the food pads would help users lose weight as they slept through a natural "trap door" in the soles of the feet.
Consumers were "guaranteed" to lose six pounds each week and up to 99 pounds in four months without dieting or taking extra exercise, the mailing said.
The product - apparently developed after 26 years of research - was described as most effective when taken over a six-week period at a cost of around £44.95.
Weight loss would be doubled if users paid extra for herbal pills, the mailing said.
The OFT contacted Post Shop, the Lebanese company behind the mailing.
Post Shop has now stopped sending out the mailing in the UK.
OFT director of consumer regulation enforcement Christine Wade warned people to be wary of "miracle claims" about weight loss.