X Factor UK viewers shocked by Simon Cowell's new look

Popular British judge Simon Cowell recently appeared on television screens over the weekend — but many fans were worried about his new look.

The music mogul is back on his judging throne for a new UK season of The X Factor.

Cowell's physique has dramatically transformed this year, as he has slimmed down on a vegan diet.

But while he judged celebrity hopefuls at his Malibu mansion, UK X Factor fans voiced their concern over his new appearance on Twitter

"Can I ask … Is Simon Cowell unwell??? He looks and sounds very unwell! Am I the only one who thinks this???????"," one person asked.

Another agreed: "Simon Cowell does not look like Simon Cowell."

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A third posted: "Simon! You need to set the record straight with fans. Are you okay? People are concerned about your recent look on TV."

"I think you look very tanned. And if you're using Botox will be a reason too. You don't need facelifts and stuff. You were fine how you were."

"Everyone's comments on twitter about #SimonCowell but has anyone thought he might be 'really' ill and something we don't know, instead of just a diet? #poorbloke."

Cowell, who is believed to have lost almost 10kg this year, changed his lifestyle after collapsing down a flight of stairs at home in 2017.

His youthful appearance was even noticed by his old X Factor sparring partner Louis Walsh.

The Irish music boss, who has returned to The X Factor: Celebrity spin-off, along with judges Sharon Osbourne and Nicole Scherzinger, jibed: "Simon's got a new face, Sharon's got a new face … this is an old face. And Nicole … ask her!"