Lady Gaga `is sick and obsessed with her weight`: journalist

Investigative journalist Ian Halperin spent 12 months studying Gaga for a new book and believes that the 25-year-old singer is 'sick' and 'obsessed with her weight'.

In an interview with star magazine, he said, 'Those who have worked with her on tour reported to me that Gaga barely ate for weeks at a time to fit into her costume.

'She is sick and obsessed with her weight. One friend told me, Gaga will stare at herself in the mirror for hours on end, analysing and critiquing her body. It's an unhealthy obsession.'

And the writer, who has penned biographies of Michael Jackson, Brad Pitt and Angelina Jolie, added that her over-the-top outfits are often designed to hide the effects of lupus.

'Her lupus is far worse than she lets on,' he said. 'Part of the reason she wears wigs and makeup is because her hair is falling out and she's covered in red blotches, both side effects of the disease.'