With a sold-out comeback residency at London’s 02 Arena in July, pop superstar Michael Jackson has reportedly been advised by doctors that he needs to bulk up. According to media outlets in the UK, the advisors to the 50-year-old “Thriller” star are worried he’s too frail to complete a full run of the “This Is It” scheduled 50 date tour.

The shows will be Jackson’s first live sets since 2001. Rumours of the pop star’s ill health have been circulating for months now – despite promoters AEG insisting Jackson is “extremely fit”. Reports, however, have doctors claiming the “Beat It” hitmaker is at least nine kilos underweight.

A source told TheSun.co.uk: “There are concerns Michael is too frail. He has been ordered to eat more but he refuses to and eats like a bird.”

Jackson’s first show kicks off on Wednesday 8 July. He’s currently rehearsing in Los Angeles, the stage production rumoured to include a duet with his 12-year-old son, Prince.