Instagram will impose tougher restrictions on posts related to cosmetic surgery and diet products.
The social media platform said both Facebook and Instagram would apply age restrictions which would stop under 18s being able to view them, while other posts would be removed all together.
The social media company has come under fire for allowing advertisers to target young people with content on impact diet, detox and cosmetic surgery products.
Activists say adverts can have a negative effect on young and vulnerable people's mental health and body image.
The new rules mean any content which makes "miraculous" claims about diet or weight-loss products linked to a commercial offer such as a discount code will also be removed from Instagram.
Emma Collins, Instagram’s public policy manager said: “We want Instagram to be a positive place for everyone that uses it and this policy is part of our ongoing work to reduce the pressure that people can sometimes feel as a result of social media.
“We’ve sought guidance from external experts, including Dr Ysabel Gerrard in the UK, to make sure any steps to restrict and remove this content will have a positive impact on our community of over one billion people around the world – whilst ensuring Instagram remains a platform for expression and discussion.”
Actress and body positivity campaigner Jameela Jamil, who has repeatedly criticised high-profile online figures including Khloe Kardashian for posting on social media about diet products, said the update was a victory for mental health advocates.
“This is a huge win for our ongoing fight against the diet/detox industry.
“Facebook and Instagram taking a stand to protect the physical and mental health of people online sends an important message out to the world,” she said.
“I’m thrilled to have been able to work towards this with them, alongside a host of other experts who shed light on the danger of these products.
“Instagram were supportive and helpful when I brought them my protests and petitions; they listened, they cared, they moved so efficiently, and communicated with us throughout the process.”
Jamil started the I Weigh movement Instagram account in response to the amount of content she felt was promoting an unhealthy lifestyle, which suggested success in life was linked to weight.
The account encouraged people to share their achievements regardless of their body shape and has since gained more than 830,000 followers.
“As someone who struggled with an eating disorder for most of my youth, I’ve personally known and suffered the perils of the devious side of the diet and detox industry,” she said.
“A focus of our advocacy since inception, it is a proud day for I Weigh and a day of hope for our generation, who deserve respect and protection from the celebrities and influencers that they follow.”
NHS chief executive, Simon Stevens, who last year called on social media firms to pay a levy towards mental health treatment linked to online activity, said: “Every business should put a premium on its customers’ well-being and it’s welcome that social media giants are beginning to listen to NHS calls to rein in harmful or misleading content that could harm users’ health.”