Note: This advice is given by the CAP Executive about non-broadcast advertising. It does not constitute legal advice. It does not bind CAP, CAP advisory panels or the Advertising Standards Authority.

The ASA and CAP receive many enquiries about marketing communications for slimming or weight control products. They include the conventional (calorie-controlled diets), the helpful (exercise regimes), the purely cosmetic (the girdle) and the ridiculous (slim-while-you-sleep-type pills and weight loss insoles). This AdviceOnline section summarises the Code’s requirements; we advise marketers to read the associated entries on “Weight control".


The main self-treatment for achieving weight loss is a slimming regime in which the intake of energy (calories) is lower than the output. Any claim made for the effectiveness of a 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 substantiation (see Rule 13.1 and the CAP Help Note on Substantiation for Health, Beauty and Slimming Claims).

Overweight is characterised in adults by a Body Mass Index (BMI) of 25-29 kg/m2 and obesity is characterised by a BMI of 30 kg/m2 or above. A BMI greater than 25 is usually associated with excess fat. Marketers should demonstrate that weight reduction is achieved by loss of body fat before any claims are made for a weight reduction aid or regimen. Weight reduction achieved through loss of water alone does not constitute a treatment for the overweight or for those who are obese. Combining a diet with an unproven weight reduction method does not justify making claims about that method (Rule 13.4). Marketing communications for slimming aids or weight reduction regimens should neither target nor appeal to consumers under the age of 18 (Rule 13.3). Marketers should not exploit the vulnerable, suggest that it is desirable to be underweight or target those for whom weight reduction is likely to result in a potentially harmful body weight (a BMI of less than 18.5 kg/m2).

Referring to precise amounts of weight loss

Claims that one could potentially lose a precise amount of weight within a stated period of time (with the exception of marketing communications for surgical clinics, 13.9) (, 5 June 2013) or that weight can be lost from specific parts of the body (The Slimline Clinic, 17 October 2012) should be avoided.

If proven, and in line with good medical and nutritional practice, marketers are likely to be able to claim that certain individuals have lost exact amounts of weight in a given period (Lifestyle Slimming, 28 May 2003, complaint 2). However, health claims that refer to a rate or amount of weight loss are not permitted in relation to food or food supplements, Rule 13.10.1 and 15.6.6). It is unacceptable to advertise that those who are overweight (but not obese) have lost more than 2lbs a week (Rule 13.10, Leslie Kenton t/a Cura Romana, 3 August 2011, The New Lifestyle Company Ltd, 17 March 2004) or that a diet based only on say, cabbage soup, is well-balanced.


Obesity in adults is defined by a Body Mass Index (BMI) of more than 30 kg/m2. Obesity is frequently associated with a medical condition and rules 12.2 and 13.2 state that marketers should not offer specific advice on, diagnosis of or treatment for it unless it is conducted under the supervision of a medical doctor or other suitably qualified health professional. (Miruji Health & Wellbeing, 2 May 2012). See on Weight control: Obesity.

Marketers must not give the impression that dieters cannot fail

Marketers should not state or imply that dieters cannot fail to lose weight (rule 13.8) or that weight loss is permanent, because the amount of weight loss that can be achieved by individuals depends on many factors and cannot be guaranteed. Examples of unaccepable claims would be: “You will lose several lbs in just a few weeks!” (Foxglove Clinic, 25 February 2004), “guaranteed easy weight loss”, “you won’t put an ounce back on”, “the yo-yo effect is permanently avoided” (Naturland RB&M Research, 3 September 2004; Equiba Institute, 28 August 2002, and H.B.R.I Institute, 10 March 2004).


Referring to short-term loss of girth resulting from a tight-fitting garment is likely to be acceptable as long as marketers do not imply that inch loss is permanent, or confuse short-term inch loss with weight loss or fat loss (Rule 13.12, Debenhams Retail plc, 17 April 2013 and MyCityDeal Ltd, 1 February 2012). See Weight control: Garments.

Testimonials and before and after photos

CAP and the ASA regard the use of before and after photographs in the same way as testimonials. Marketers should ensure that they meet the requirements of rules 3.45 to 3.48 of the CAP Code. They should hold signed and dated proof that the photos are genuine. However, robust evidence should still be held to prove claims that consumers are likely to regard as objective (Debbie's Wraps, 26 March 2014). See Weight control: Testimonials and Before and after photos.

Food, soft drinks and supplements

Marketers promoting a food (or a soft drink) or food supplements in relation to weight should take the Food Rules into account and note that weight loss and other claims of this nature, which directly result in an effect on one’s health, are likely to be considered health claims for the purposes of Section 15 of the Code. A health claim for a food should not be made unless that claim is compatible with an authorised claim listed on the EU Register of nutrition and health claims (NAH Foods Ltd, 31 July 2013 Marketers may however, offer dietary supplements as a safeguard to adequate intake as long as they do not attribute weight loss to vitamins and minerals (Rule 13.6).

Marketers may offer dietary supplements as a safeguard against any shortfall in recommended intake when dieting, as long as they do not attribute weight loss to vitamins and minerals (Rule 13.6). See Weight control: Food and Food supplements

See Medicinal Claims, Weight control: Testimonials, Claims in names, and other entries under "Weight Control".

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