Isabelle Caro, a French model who became a symbol of the fight against anorexia when she was photographed naked for a controversial advertising campaign, has died at the age of 28. Caro rose to global prominence three years ago when posters featuring her emaciated body were displayed around Milan on the eve of fashion week, sending shockwaves through an industry criticised in some quarters for failing to tackle eating disorders among its models.

The posters were banned by the Italian advertising watchdog but the images went viral online, sparking a debate just months after the deaths of two prominent Latin American models.

Caro, who had struggled with anorexia since she was 13, chose to battle her demons in public in a bid to warn women away from the disease. She appeared on talk shows and wrote a blog and then a book titled The Little Girl Who Didn't Want to Get Fat.

She died on 17 November after returning to France from a job in Tokyo but news of her death was kept secret until this week.

The exact cause of death is not known but she was treated in hospital for a fortnight with an acute respiratory disease after returning from Japan. Her family held a private funeral in Paris. Referring to Caro's anorexia, Daniele Dubreuil-Prevot, her long-time acting instructor, said the French model "had been sick for a long time".

Vincent Bigler, a Swiss singer who became a close friend of Caro, told The Independent that Caro had been determined to help women like her who suffered from eating disorders.

"She was this thin girl with a fragile voice but inside she was amazingly strong," he said. "She was always very close to people like her. She would give out her phone number to anyone who wanted to talk about eating disorders. She even put her number on her blog. On her birthday this year she invited all her followers and fans to her party. That was the kind of person she was. She was very open-minded."

Bigler had got to know Caro personally after writing a song about her called "J'ai fin," a wordplay that roughly translates as "I'm done" but is also near-identical to J'ai faim, the French for "I am hungry."

In a video tribute posted on YouTube yesterday he wrote: "Thank you Isabelle for your courage and for the messages you passed on. I hope that up there you enjoy what you love: art, poetry, reading and the love of others."

Caro's poster campaign caused anger among some campaigners who feared that her skeletal image might inspire young women rather than encourage them.

On "thinspiration" internet forums yesterday there were a number of tributes glorifying the model's anorexia problems. One blog placed a picture of a painfully thin looking Caro alongside the words "die young, stay pretty".

But Caro had always rebuffed such criticism, saying she believed most young girls would be repulsed and not encouraged by the poster campaign.

"My anorexia causes death," she explained in an interview three years ago. "It is everything but beauty, the complete opposite. It is an unvarnished photo, without make-up. The message is clear – I have psoriasis, a pigeon chest, the body of an elderly person."

The Italian photographer Oliviero Toscani, who shot the hard-hitting campaign, made a similar argument. "Looking at my ad, girls with anorexia would say to themselves that they have to stop dieting," he said at the time. "When you do something extreme, there are always people who oppose it. It shouldn't be the photos that shock, but the reality."

Yet despite her public determination to combat anorexia, Caro still struggled to fully overcome the disease. At the time of the campaign she weighed just 29 kilograms and had fallen into a coma the previous year.

Last year she was interviewed by the American pop star Jessica Simpson and said her weight had risen to 39 kilograms, but she still looked painfully thin. During the interview she told Simpson how she had started modelling during her last year of high school and had been immediately told to lose 10 kilograms. Despite her obviously frail physique she said she had never once been told by a modelling agency to put on weight.