Instagram is bringing in tighter restrictions on some posts on the site.
They'll be imposed on any that are about diet products and cosmetic surgery.
On both Instagram and Facebook, age restrictions will now be applied to some posts on the subjects, while others will be removed.
The social media site says that its new rules mean posts which promote certain weight-loss products or cosmetic procedures which encourage people to buy it, or which include a price, will be hidden from users known to be under 18 years old.
The platform has also said that any content which makes a "miraculous" claim about a diet or weight-loss product, and is linked to things like discount codes, will now be taken down.
Actress and body positivity campaigner Jameela Jamil, who has criticised some celebrities for posting on social media about diet products, said "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."
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."
There are lots of charities that provide support to young people with mental health worries, including the NSPCC, YoungMinds and the Children's Society.
If you are upset by what you see on social media, make sure you talk about how you are feeling with friends or a trusted adult.
If you are struggling and there is no one you feel you can talk to about it, you can call Childline for free on 0800 11 11. This number does not show up on your phone bill.