A new book is claiming that Lady Gaga starves herself in order to fit into her costumes, said Britain's Daily Mail.

The book - Poker Face: The Rise And Rise Of Lady Gaga, by the singer's former tour manager, Mr David Ciemny - says Gaga was hospitalised six times last year due to her yo-yo dieting.

Mr Ciemny says that the star goes to dangerous lengths in order to stay skinny, said the Mail.

He writes in his book that Gaga would go on junk-food binges while on tour and would gorge on sweets and unhealthy food. Then, she'd not eat for weeks in order to slim down. He recalls that she once lost 9kg between fittings, said the Mail.

Her weight had reportedly been the subject of concern when she shot her music video for Paparazzi.

A witness from the shoot said: "Producers had to shoot around her. They draped fabric over her thighs and shot her backside with a softer lens."

Gaga has other health issues to worry about.

In January, she was forced to cancel four US shows after suffering from an irregular heartbeat brought on by exhaustion, noted the Mail. She also tested "borderline positive" for Lupus, a tissue disease which claimed the life of her aunt.

Following a severe case of jet lag after arriving in Australia, Gaga passed out three times while performing her first show in Auckland back in March, said the Mail.