The duchess - who is an ambassador for dieting company WeightWatchers - stayed in a bed and breakfast in Hull, East Yorkshire, so she could be close to a family of seven struggling with their weight who were taking part in her documentary about obesity.
Sarah Ferguson, the Duchess of York, moved into a £40-a-night hotel in one of the poorest areas in Britain to experience life on benefits.
The duchess - who is an ambassador for dieting company WeightWatchers - stayed in a bed and breakfast in Hull, East Yorkshire, so she could be close to a family of seven struggling with their weight who were taking part in her documentary about obesity.
Mick and Tonia Sargerson and their five children live on the Preston Road Estate, which has one of the lowest income levels in Britain.
Sarah said: "Weight issues are common across all paths of life, in all kinds of people. But I know that the Sargerson family live in a way I hadn't experienced.
"What is it like to live on benefits with £80 a week to feed seven people? To talk about it but not live it would be wrong of me. So I went to live with them - well, I actually slept in the B+B down the road, but spent all my time with them, so I could understand."
The duchess - who has two children Princesses Beatrice and Eugenie with ex-husband Britain's Prince Andrew - also revealed she and Tonia became "kindred spirits".
She told Psychologies magazine: "When we first met we looked at each other for a moment and then she put her arm around me and said, 'We are the same aren't we?' We both felt it.
"It didn't really matter about the difference in our circumstances. It doesn't matter who you are if you have a weight problem or you feel as though you can't live with the poor self-image of yourself. She and I became kindred spirits."
Sarah Ferguson
Duchess of York
