Image caption Matt says he posted his transformation to inspire others

A personal trainer says photos he posted on Instagram to mark his fitness transformation were taken and re-posted by fake accounts to promote diet pills which he had never taken. He told the Victoria Derbyshire programme such companies feel they are untouchable.

"It was a big deal for me to put that photo online," says Matt Lindsay, a personal trainer based in London. "I put myself in a vulnerable position in good faith to inspire others - with sensible eating and sensible nutrition and hard training."

He was contacted by clients who spotted the before and after pictures of his physique on an Instagram account which shares memes and has millions of followers.

The post, which was liked more than 4,300 times, said: "SHOCKING discovery has helped so many people transform their bodies that for a limited time only."

The post also offered free trials to new customers.

Mr Lindsay contacted the Instagram account directly and asked it to remove his picture, which it did. But he was unable to report the company associated with the advert as there were no contact details on the website.

He says he is concerned about the impact on his reputation: "I don't like my face being a cover for something that is dangerous for people," he says. "I did not post my photo to plug a quick fix.

"They can say anything they want about me and I can't do anything about it - they feel untouchable."

Anything you post on the internet is only ever a cut and paste away from being copied and posted repeatedly, and could end up in places you might never have chosen yourself.

You only have to look at the social networks' struggle to contain copies of horrific content - like the 1.5 million copies of the video of the New Zealand shooter that Facebook removed in the first 24 hours after the attack - to understand the scale of the problem.

Even the tech giants, with all the cash they have to throw at preventative measures, find it difficult to manage.

Moneysaving expert Martin Lewis settled a defamation lawsuit against Facebook in January, after thousands of adverts using his name and image as fake endorsements appeared on the platform.

Mr Lewis has never done ads.

The law states that a photograph you have taken is your intellectual property and is copyright protected - only you have the exclusive right to reproduce the image.

But digital lawyer Heather Anson says an individual no longer owns an item once it has been uploaded to social media. It then belongs to the platform, and people cannot be stopped from downloading and using it.

But, she adds, other laws can be considered if the images are used for commercial purposes.

"New EU copyright laws around memes and image-sharing have enforced photos being taken down," she says, "including added responsibility for the social media platforms themselves when it comes to copyright - they are much more proactive."

People can complain to the ASA via an online information form, or go to the ICO (Information Commissioner's Office).

Ultimately, if someone uses your photo without permission, you can bring legal proceedings against them for copyright infringement - but this hinges on whether or not you have the time, effort, money and inclination to sue.

Bogus claims

A number of people have reported seeing their photos lifted and used for advertising on accounts which use fake identities or stories.

The Duchess of Sussex has been the subject of bogus claims which stated she used "Keto Weight Loss" tablets. The adverts used photos of her before and after her pregnancy.

CJ Brough, a casting director for brand campaigns, says no brand should use an image without permission. But she says there is not a lot Mr Lindsay can do, as it was unlikely to be worth suing over a small campaign for this kind of company.

"His best bet for 'revenge' is to use the community spirit of Instagram to support him," she says. "If he was to say what happened to him, he would probably face a lot of support."

But she said brands taking images in this way can be useful for people trying to build a social media profile, adding that what happened to Matt was one of the natural pitfalls of social media.

"If you're tagging M&S and wearing an M&S dress, it's not so much a grey area," she explains. "People want this to happen, putting time and effort into creating content and attracting potential brand partners. That's your stepping stone to how you might get contracts as a brand."

The companies involved in Matt's case were approached for comment, but none of them replied.

Instagram recently announced it is clamping down on posts which promote diets and cosmetic surgery.

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