Britney Spears is reportedly busy preparing for this coming weekend's X-Factor performance - by not eating.

The singer has apparently set her sights on bringing her own X-factor to the UK this Saturday by down-sizing her already svelte figure.

But the effects have been far from positive and have left friends fearing for her health.

A source tells the Daily Mail, "She goes to bed hungry and is dieting so hard she's suffering from insomnia, anxiety, flushes and shakes.

"Her father and the people around her are trying to get her to eat more, but Britney is determined not to be criticised for having any extra bulk."

Meanwhile Simon, the other judges and the UK public are all on the edge of their seats for Brit's first televised appearance in the UK in five years.

Will it live up to the hype? Stay tuned.

See Britney's best VMA performances below