Notorious for her weight fluctuations, the Duchess of York has revealed her latest method for shedding the pounds – mandarins, tomatoes and egg mayonnaise.

Fergie has lost more than three stone and kept it off for almost three years, and says the bizarre food combination “works for her”.

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Prince Andrew’s ex-wife has in the past lost weight through eating a healthy diet, and doesn’t reveal the other foods that have helped her keep the weight off.

However the Duchess, 57, stresses that she has a strict fitness regime too, going for daily runs and mountain hikes in the Swiss Alps, where she spends a lot of her spare time.

Staying slim has never been easy for Fergie, who says she started comfort-eating after her parents separated when she was a child. But although she admits food has remained an addiction throughout her adult life, she told a magazine: “I became obsessed with food. Luckily it was food and not any other addiction.”

Celebrity diets

Fergie isn’t the only celebrity to have embarked on unusual diets in a bid to lose weight or simply feel healthier, Beyonce eliminates all animal products from her diet when she wants to detox and lose weight, and Angelina Jolie has used the ancient grains diet, where she adds plenty of grains including quinoa and millet, nuts and seeds, to what she eats whenever possible.

Singer Katy Perry and actress Kelly Osbourne are said to have lost weight by following the M-Plan diet, incorporating plenty of mushrooms into their lunches and dinners over a 14-day period. The diet claims to help women lose weight from their tummy, bum, thighs and upper arms, without affecting the bust.

[Read more: The top 5 worst celebrity diets to avoid]

The expert verdict

Dietician Dr Carrie Ruxton points out that the Duchess of York’s weight loss was over a long period, which is definitely the best way to do it.

“The Duchess’ weight loss is a good, steady amount and shows her diet wasn’t faddy,” she says.

“A slower weight loss tends to stay off, while extreme dieting just leads to weight rebound, where you gain what you lost plus a bit more.

“I’m sure the Duchess was eating more than eggs, mandarins and tomatoes and, of course, taking regular exercise to achieve her weight loss. However, these are healthy foods with nutritional benefits.”

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Mandarins are high in vitamin C, which supports skin, bones and immune function, while tomatoes contain the antioxidant lycopene, which protects body cells against damage caused by things like ageing, cigarette smoke and pollution.

Eggs are high in protein and have been shown to boost satiety so we feel fuller after meals, helping people avoid snacking.

Ruxton says boiled or poached eggs are best, but she advises: “I would tend to have eggs without mayo, as it’s high in fat and salt.

“Eggs are no longer limited by health professionals as they’ve been proven not to raise blood cholesterol levels, so have them several times a week if you like.”

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