People who wish to lose weight have been warned to stay away from social media influencers who claim to have the latest diet fix, researchers say.

A study by a team at University of Glasgow found that just one out of nine leading UK bloggers making weight management claims actually provided accurate and trustworthy information.

The health researchers studied the country’s most popular influencers, based on those who had more than 80,000 followers on at least one social media site, verification from at least two sites such as Twitter, and who had an active weight management blog.

Lead author Christina Sabbagh said: “We found that the majority of the blogs could not be considered credible sources of weight management information, as they often presented opinion as fact and failed to meet UK nutritional criteria.

“This is potentially harmful, as these blogs reach such a wide audience.”

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Although the social media stars were not named in the study, blogs by nine top influencers published between May and June 2018 were analysed and scored against 12 criteria to demonstrate credibility.

The university team examined whether the health and diet claims made by influencers were transparent, trustworthy, nutritionally sound and included evidence-based references. They also looked at the role of bias in what was put online.

Influencers were regarded as having “passed” the test if they met 70 per cent or more of the criteria. Researchers also examined the latest 10 meal recipes from each blog for energy content, carbohydrates, protein, fat, saturated fat, fibre, sugar and salt content.

The findings – presented at this year’s European Congress on Obesity (ECO) in Glasgow – showed that a majority of bloggers failed in fundamental areas.

Five of them presented opinion as fact or failed to provide evidence-based references for nutritional claims. Five failed to provide a disclaimer and, when meals were examined against Public Health England calorie targets and traffic light criteria, no blogger met these criteria.

Of the advice-based blogs, only one by a registered nutritionist with a degree passed overall, with 75 per cent. The lowest compliance, 25 per cent, was from an influencer without any nutritional qualifications.

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The authors concluded: “Social media influencers’ blogs are not credible resources for weight management. Popularity and impact of social media in the context of the obesity epidemic suggests all influencers should be required to meet accepted scientifically or medically justified criteria for the provision of weight management advice online.”

Tam Fry, chairman of the National Obesity Forum, said: “This study adds to the evidence of the destructive power of social media. Any Tom, Dick or Harry can take to the ether, post whatever they like and be believed by their followers.

“Particularly unfortunate is that the genie is now firmly out of the bottle and getting these bloggers to conform to standards, though desirable, will be nigh impossible.