Weight and slimming

Helpful information on the advertising rules for weight-loss and slimming products and examples of previous Advertising Standards Authority rulings in this area.

Ads for weight-loss and slimming products are allowed to sell us a dream or aspiration, but advertisers need to make sure their claims have a firm foundation in reality. Most of the complaints we receive about weight-loss and slimming products are related to the capability of the product, and this capability being exaggerated in the ad.

The advertising rules state any claim made for the effectiveness of a weight-loss or slimming method or product should be backed by rigorous practical trials conducted on people. Testimonials that are not supported by trials do not constitute adequate evidence.

Claims that specify a precise amount of weight-loss within a specific time period should be avoided. As should claims that state a weight-loss or slimming product can help you lose weight from a specific part of the body.

As well as making sure their ads are honest and don’t mislead consumers, advertisers marketing weight-loss or slimming methods or products should ensure their ads do not exploit vulnerable groups and are prepared with a degree of social responsibility. Ads shouldn’t be targeted at, or appeal to, consumers under-the-age of 18 or those for whom weight reduction is likely to result in a potentially harmful body weight. Ads should never suggest that it is desirable to be underweight.

Furthermore, it is important for advertisers to remember the amount of weight-loss that can be achieved by an individual depends on many factors. It is not the same for everyone and it cannot be guaranteed. This should always be reflected in ads for weight-loss and slimming products and that is why the advertising rules say you cannot state or imply that dieters can’t fail to lose weight when using your product, or that weight loss is permanent.

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Latest rulings

Marks and Spencer plc
- Upheld in part
- Email, App (own claim), Website (own site)
- 23 July 2025
A page within the Marks and Spencer app was socially irresponsible by portraying a model as unhealthily thin. A website, email and second app page were also investigated but did not break the rules.
Asos.com Ltd
- Not upheld
- App (own claim)
- 16 July 2025
An in-app ad for a clothing company, was not irresponsible and did not promote an unhealthy body image.
Chequp Health Ltd
- Upheld
- Social media (paid ad)
- 09 July 2025
A paid-for Meta ad for weight-loss treatments promoted prescription-only medicines to the public, against the law and our rules.
Express Healthcare Ltd t/a pharmacyonline.co.uk
- Upheld
- Search (paid)
- 09 July 2025
A paid-for Google search ad for obesity treatment jabs promoted prescription-only medicines to the public, against the law and our rules.

View all rulings

Weight and slimming

Helpful information on the advertising rules for weight-loss and slimming products and examples of previous Advertising Standards Authority rulings in this area.

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Relevant codes

12 Weight control and slimming

13 Weight control and slimming