Major retailers and online marketplace are making "outlandish claims” to market weight-loss supplements, a watchdog has warned.

Which? said it found evidence of Amazon, eBay, Holland & Barrett, Superdrug and Temu among others using "misleading" claims to advertise weight-loss supplements.

One example is Extreme Burn supplements by a business called Formula Max 5 listed on eBay, which carried the claim that raspberry fruit extract “assists the body to burn fat at a higher rate” and the addition of green coffee bean “decreases the absorption of carbohydrates”.

But experts have told the* Independent *that there is little evidence to suggest these supplements are reliable weight loss drugs.

Holland & Barrett and Superdrug were also found to have product categories on their websites for “fat burners” and “appetite suppressants”, despite the fact some of the tablets listed in these categories did not make any weight loss claims. Other products listed on Temu claimed to target fat loss in specific areas of the body.

The watchdog has called for “better oversight” of the industry so regulators can crack down on these misleading listings.

Which? said it found evidence of Amazon, eBay, Holland & Barrett, Superdrug and Temu among others using ‘misleading’ claims to advertise weight-loss supplements (stock image) (Getty Images/iStockphoto)

The health claims register, held by the Department of Health and Social Care (DHSC), shows what businesses can – and cannot – say an ingredient can do for people’s health, with the wording and conditions for its use often specific.

A number of weight loss claims for raspberry extract were all rejected by the health claims register owing to a lack of compelling evidence, while the green coffee bean claim that it “acts by reducing the absorption of sugar (glucose) from the digestive tract” was also rejected.

“There are a lot of claims that ‘raspberry ketones’ can result in weight loss by increasing burning of fat - but there is not really that much evidence that it actually works,” Gunter Kuhnle, Professor of food and nutritional sciences at Reading University told the Independent.

He explained that in the green coffee bean supplement one compound called chlorogenic acid can reduce carbohydrate absorption, but he stressed that many other foods also have this property.

“At best, these ingredients may have minor metabolic effects and at worst, they risk misleading people into thinking supplements can replace proven approaches like diet quality and energy balance,” registered nutritionist Rob Hobson told the* Independent.*

Which? said it also saw products listed for sale on online marketplaces that claimed to target certain areas of the body or be as effective as weight-loss jabs - which goes against advertising regulations.

The Advertising Standards Authority (ASA) states that products cannot say how much weight customers could lose or how quickly, or from which part of the body, as this was something brands could not predict. They also cannot claim to provide effects associated with prescription-only weight loss drugs.

But Which? Found a “keto fat burner” supplement from the brand Pslalae on Temu claiming that customers would “lose your belly fat fast while you shred your stomach”. Another supplement from the brand Coolkin sold on Temu, claimed it could “reduce waistline”. Similarly, a product called “Gone Appetit”, from Internal Youth on Amazon, suggested that within four weeks “you’re losing centimetres from your waistline”.

Another listing for the product Phentramine 375 by Pharmaslim on eBay read: “Why use prescription weight loss pills when you can get non-prescription weight loss pills that have no negative side effects but are just as effective?”

Which? said it reported all its findings to the retailers, which it claimed had led to more than 50 “misleading” weight-loss supplement listings being taken down.

A Government spokesman said: “Any claims about the health benefits or nutritional value of supplements need to be backed by science and officially approved by authorities.

“Companies that break these rules may be subject to enforcement action by local authorities.”

Amazon, eBay and Temu said they have reviewed the listings and removed the highlighted products that go against their policy.

Holland and Barrett explained product categorisation is intended to support customers to navigate our website, but following a review it has moved products to the “superfood category".

Superdrug has paused all retailing of the highlighted product and is reviewing the category on its website.

Coolkin told Which?: “Our products are certified before they are put on the shelves. There is no problem.”

A Pharmaslim spokesman said: “The product is manufactured in the UK in a licensed facility and is a food supplement, not a medicinal product. We do not make medical or therapeutic claims for it.

“For completeness, the listing you are referring to is not currently active, as the product is out of stock. We are reviewing the points you raise regarding product naming and marketing presentation.”