He's dramatically overhauled his lifestyle this year after a health scare.

And Simon Cowell was looking trimmer than ever as he posed on the red carpet ahead of the America's Got Talent quarter finals on Tuesday night.

The music and TV mogul showed off his 20Ibs weight loss, as well as his megawatt smile, during the pre-show photocall at Hollywood's Dolby Theatre.

Transformation: Simon Cowell was looking trimmer than ever as he posed on the red carpet ahead of the America's Got Talent quarter finals on Tuesday night

Dressed in a tight-fitting grey sweater and loose black trousers, Simon flaunted his slimmed-down physique before heading inside the theatre to judge the anticipated quarter final performances.

Simon's appearance comes after he spoke candidly about changing his lifestyle and diet after he was hospitalised in October 2017 after fainting as a result of low blood pressure.

Speaking to Extra TV in June Simon said: 'I went to see this guy who's very well-known. And he said to me, after doing some blood work, 'You can't have red meat, dairy, sugar, bread or gluten'.'

Makeover: The music and TV mogul showed off his 20Ibs weight loss, as well as his megawatt smile, during the pre-show photocall at Hollywood's Dolby Theatre

The X Factor boss admitted that his first thought following the advice was 'What about alcohol?'

He continued: 'And he said, 'Maybe not quite as much as you had before'. And I did it and I stuck to it and it's easy.'

Simon, who now lives a much healthier lifestyle with his partner Lauren Silverman, 42, and their five-year-old son Eric, and has also joked that he and his little boy follow the same vegan diet.

Trim: Dressed in a tight-fitting grey sweater and loose black trousers, Simon flaunted his slimmed-down physique before heading inside the theatre

Head judge: Simon is having a busy summer jetting back and forth between the US and UK for work on his talent shows

Health scare: Simon's appearance comes after he spoke candidly about changing his lifestyle and diet after he was hospitalised in October 2017 after fainting

New diet: Simon is sticking to a vegan diet, cutting out red meat, dairy, sugar and gluten

'Apart from ice-cream, he actually likes water, eats all his raw vegetable. I'm on the Eric Cowell diet,' he pointed out.

Simon is having a busy summer jetting back and forth between the US and UK for work. While he wraps up the current series of AGT, he's also presiding over Britain's Got Talent: The Champions which will see former winners and finalists compete against each other.

The show will air in the autumn, with Simon and his team busy filming the auditions in recent weeks.

Cutting back: The star has also cut back on alcohol, after admitting it was contributing to his poor diet and lifestyle