Michael Jackson has been advised to bulk up some muscle so he is strong enough to perform in London.

The 50-year-old singer, who starts a 50-date residency at the O2 Arena this summer, has been told he is currently "too fragile" to go ahead with the gigs because his BMI is too low.

A source told the Mirror newspaper: "Docs are worried he won't have the strength to perform. He's been told to drink protein drinks called Metric to beef up."