The Sun report that doctors said Wacko is 20lb underweight and needs to bulk up before his 50-date run of performances, which will include his famous dance routines.
The 50-year-old King Of Pop is also battling an old back injury, takes antibiotics for a skin infection and wears a mask when he goes out to keep bugs at bay. Not exactly the picture of health, poor thing.
The Sun quote a source as saying: "There are concerns Michael is too frail. He has been ordered to eat more but he refuses to and eats like a bird.”
The shows will mark Wacko's first performance since a dodgy stint at the 2006 World Music Awards, where he only managed to sing a few lines of 'We Are The World'.
Reports say he is insisting on having live animals with him on stage and is planning to perform with his 12-year-old son Prince.
Check out the evolution of Michael Jackson in our gallery below!