Fans shocked at Simon Cowell's dramatic weight loss

Simon Cowell has taken to the red carpet to show off his trimmer figure, but fans are shocked by his appearance.

The musician mogul lost 10kg after adopting a vegan lifestyle, but people have been taken aback by his drastic new look.

Cowell looked drastically different in August 2018. Photo / Getty Images

"He looks like a very bad lookalike of himself," one wrote on Twitter.

"Someone should check Madame Tussaud's (to see) if they are missing wax sculpture," wrote another.

According to The Sun, the 59 year old was instructed to make "drastic lifestyle changes" after falling down the stairs in the middle of the night in October 2017."

He was reportedly rushed to hospital and told he had to stop bingeing on sausage rolls, hamburgers and his favourite jam tarts made by his personal chefs.

Simon Cowell looked slimmer than ever on Tuesday night as he made a rare red carpet appearance for the America's Got Talent quarter finals. Photo / Getty Images

Doctors also warned against him living "like a vampire" by staying awake all night every night until 8am - saying it had to stop.

"Within 24 hours I changed my diet and I've not looked back since. You feel better, you look better, the America's Got Talent judge told The Sun earlier this year.

The father of one went on to explain he's since cut meat, dairy, wheat and sugar out of his diet.

"Once you get into a pattern I've found it quite enjoyable. It has helped me sleep and I wake up feeling less tired.