Princess Diana had addressed her eating disorder during the BBC Panorama interview and it was also written about by her biographers.
Trigger warning: Graphic details about Bulimia Nervosa.
We attach a lot of value to what our partners say about us and to us. Especially, when we are young and impressionable, others' opinions of us matters a lot more. And Princess Diana at 20 was definitely young, and maybe impressionable too. Her much-older partner Prince Charles' statements would have made a huge impact on her.
Diana and Charles married a few weeks after her 20th birthday. The prince was 32 at the time, and instead of being careful with his words, he left her scarred. In Diana: Her True Story – in Her Own Words written by author Andrew Morton, she is quoted as saying that Charles' off-hand remark about her body triggered something inside her, writes People.
After she passed away, it was found that she was the "source" for the book and had spoken through tapes given to Morton by her friend, James Colthurst. The book talks in detail about her private struggle with bulimia, an eating disorder. The Netflix show The Crown also shows Diana suffering from this mental health crisis.
"The bulimia started the week after we got engaged (and would take nearly a decade to overcome),” Diana had recorded herself saying. "My husband [Prince Charles] put his hand on my waistline and said: 'Oh, a bit chubby here, aren’t we?' and that triggered off something in me. And the Camilla thing," she had said. Diana was referring to Charles' affair with Camilla Parker-Bowles, who was married to Andrew Parker-Bowles at the time and is now married to Charles.
"I was desperate, desperate. I remember the first time I made myself sick. I was so thrilled because I thought this was the release of tension," the Princess of Wales said. "The first time I was measured for my wedding dress, I was 29 inches around the waist. The day I got married, I was 23½ inches. I had shrunk into nothing from February to July. I had shrunk to nothing," she said.
Even Elizabeth Emanuel, the designer of Diana’s wedding gown, revealed that between the first fitting and the last, she had lost 3-4 inches, as per Vogue. A royal commentator later said that it was her difficult marriage that triggered the mental health crisis in her.
"Bulimia nervosa, the eating disorder Diana developed within a year of becoming Princess of Wales, was not (as Charles’s friends have suggested) an illness which made a marriage go sour," wrote Anthony Holden in a 1993 issue of Vanity Fair. "It was an illness caused by a sour marriage."
In 1995, Diana spoke about her illness during the BBC Panorama interview with Martin Bashir, who is now being investigated over it. He asked her if she suffered from the illness.
"Yes, I did. I had bulimia for a number of years. And that's like a secret disease. You inflict it upon yourself because your self-esteem is at a low ebb, and you don't think you're worthy or valuable. You fill your stomach up four or five times a day—some do it more—and it gives you a feeling of comfort. It's like having a pair of arms around you, but it's temporary, temporary. Then you're disgusted at the bloatedness of your stomach, and then you bring it all up again," she said.
She was asked if she had ever revealed this to anyone in the royal family, and she said she hadn't. It shows how lonely she had been in her struggles while being part of the British monarchy.
"You have to know that when you have bulimia you're very ashamed of yourself and you hate yourself—and people think you're wasting food—so you don't discuss it with people," she explained. "The thing about bulimia is your weight always stays the same, whereas with anorexia you visibly shrink. So you can pretend the whole way through. There's no proof."
It took Princess Diana years to get over it, and perhaps being released from her marriage helped her be free of the disease too.
Disclaimer: Bulimia Nervosa can be life-threatening if not treated in time.
References:
https://www.vogue.com/article/princess-diana-real-life-battle-with-bulimia
https://www.vanityfair.com/magazine/1993/02/princess-diana-revenge-anthony-holden-cover