Jameela Jamil has called Kim Kardashian West a “toxic influence” for posting an advert promoting a dieting lollipop.
The reality TV star shared a photo of herself eating the product – which it’s claimed suppresses your appetite – onto Instagram.
Jameela, who has a social media campaign around body positivity, described her a “terrible and toxic influence on young girls”.
Newsbeat has contacted Kim’s representatives for a comment.
“Maybe don’t take appetite suppressors and eat enough to fuel your brain and work hard and be successful,” Jameela wrote in Twitter.
“And to have something to say about your life at the end, other than ‘I had a flat stomach’.”
Jameela is the founder of the I Weigh social media campaign – which encourages men and women to focus on achievements other than looks and weight.
When she spoke to Newsbeat about it in March, the 32-year-old said she’s been a “body positivity warrior” for a long time.
The product Kim is advertising is from a company which sells diet products, including the appetite suppressant lollipops.
The company’s website says the lollipops are designed to be taken when people experience food cravings.
But there is a disclaimer which says: “These statements have not been evaluated by the Food and Drug Administration.”
The same company has had social media adverts banned in the UK.
In September last year, the Advertising Standards Agency (ASA) told the company to take down an ad from Geordie Shore’s Sophie Kasaei’s Instagram.
The ASA said that the ad’s health claims weren’t approved by EU regulations.
It also removed an advert for the same product in April 2017 from makeup blogger Sheikhbeauty because it wasn’t clear that the Instagram post was a paid promotion.
Newsbeat has contacted Flat Tummy Co for a comment.