The authority said the claim, which appeared in a print advert for Atkins Nutritionals, could not be proved as there was no evidence to suggest the diet offered any long-term benefits. Atkins had supplied 44 scientific studies which it believed supported the claim.
The advert, which showed a range of Atkins products, including shakes, snack bars and salads, also fell foul of UK government advice that states a healthy balanced diet should include starchy foods, which are cut from low-carb diets.
The ruling is yet another blow for the low-carb diet, which has come under increased criticism from nutritionists and the industry in recent months.
According to findings published last week in The Grocer, many retailers now prefer to market products as low Glycaemic Index, which is believed to be a more credible way of monitoring carbohydrate intake than the Atkins approach.