SARAH Ferguson has told how she shifted three stones after realising she was close to the weight she had reached while pregnant.
And she has told how criticism of her battles with her weight made it difficult to go out in public and hurt her, reaching into the "depths of my soul".
In an interview with Hello! magazine, she also spoke about how she felt she was "drowning in food" as she struggled to control her eating.
Ms Ferguson (54), who was at one stage a Weightwatchers ambassador, dropped her weight over a period of five months by cutting out sugar and sticking to a regular exercise regime.
She said she was prompted to take action when she realised she was nearly as heavy as when she was pregnant with the first of her two daughters, Beatrice, who is now 25.
"That's what really frightened me," she said. "Beatrice was an 8lb 8oz baby and I was only 6lb off my full-blown pregnancy weight.
"I used to be so angry. I believed I was never going to lose the weight, that I had lost control. I couldn't fit into any of my clothes. I was just drowning in eating, drowning in food.
"It took courage to go out in public in all the years I have been overweight. Every time there was a "Duchess of Pork" or "Fat Frumpy Fergie" headline, they didn't have any idea they were reaching to the depths of my soul."
Ferguson has been appointed as an ambassador for the Institute of Global Health Innovation at Imperial College London.