Jameela Jamil says there's an "epidemic of low self-esteem" for girls and women across the world because of social media.
The actress and presenter has started a campaign called "I Weigh" to celebrate people's achievements rather than their weight.
Jameela says she wants to inspire women not to focus on the way they look.
"Every minute we spend thinking about how thin and gorgeous and perfect we aren't, is a moment that we aren't thinking about growing our business or our education, or our family or the fun in our lives," she tells Newsbeat.
She's not the first person to encourage people not to focus on their looks, but the 32-year-old says she's been a "body positivity warrior" for a long time, and especially since her days presenting the Official Chart Show on Radio 1.
"I'd gained 200,000 listeners which was great, and the papers on that day - instead of reporting that - reported that I'd gained two dress sizes and had loads of photographs fat shaming me and ridiculing my body," she says.
But it was an Instagram account with hundreds of thousands of followers that inspired I Weigh, when it posted a picture of the Kardashian sisters next to how much they weighed.
"I just thought - why do we care so much about this? When women have come so far in life why are we still being told to care about this?"
Jameela's response turned out to be the start of I Weigh - which encourages people to post positive messages that don't relate to their appearance.
Women and girls looking at airbrushed and Photoshopped images on social media are who the account is primarily for.
"I'm hearing about eight-year-olds and nine-year-olds worried about their bodies and their thighs, and their thigh gaps. It's just out of control," Jameela says.
"At least before it used to just be celebrities, but now it's people trolling each other on Instagram, or glamorising being anorexic."
The Good Place actor wants Instagram influencers to acknowledge the role they can play in making young women feel self conscious with "irresponsible" posts.
"They don't know that these girls starve themselves, they don't know how much these girls work out to look the way they do - because these girls just post pictures of themselves eating massive slices of pizza and just sort of lounging around hotel balconies."
"We have to unfollow people who make us feel bad about ourselves and who promote unrealistic lifestyles and body standards on the internet," says Jameela.
Men have been getting involved as well.
The presenter says she's been part of campaigns that tell women to "celebrate your cellulite and your bingo wings and whatever", but wants I Weigh to be more than that.
"I think that's great, but I also think that still keeps us in the conversation about what we look like."
The campaign has been surprising for Jameela because of the lack of trolling it has received - and the inspiring posts she's been sent.
"Women are just going: 'I'm struggling, and that is part of what makes me a beautiful and worthwhile individual, and these are all the things that I love that have nothing to do with my exterior.'"
But it's also been sobering in some ways.
"Some women can't even do an I Weigh page.
"They say: 'I love your campaign and I'm so inspired by it but I can't think of anything nice to say about myself because I'm so sad that I'm not thin and beautiful.'
"We are in crisis."
If you're struggling with your mental health or an eating disorder you can find help at BBC Advice.