Simon Cowell's girlfriend thinks he looks ''so awesome''.

The 59-year-old entertainment mogul has shed 20lbs since going on a strict vegan diet and Lauren Silverman - with whom he has five-year-old son Eric - is a big fan of his new look.

She gushed to 'Extra': ''He's so thin, he looks so awesome.''

On his diet, Simon has cut out dairy, sugar, bread, gluten, and meat and won't even let the regime slack on his 60th birthday next month.

He vowed: ''No cakes. There will not be a birthday cake.''

The 'America's Got Talent' judge recently admitted he drastically changed his diet so he could keep up with his son.

He said: ''I went to see this doctor in London. We did some tests. And then a month later he said, 'You have the worst diet I've ever met from any patient.' So I went, 'Okay, out of the smoking, the drinking, and diet, what do I have to drop?' And he said, 'The diet.' So I said, 'I'm in!'

''It was easier than I thought, and part of the reason I did it was because of Eric. I realised if I didn't sort myself out physically, I wouldn't be able to catch up with him. Because the minute he gets up to the minute he goes to sleep ... their energy, you forget, at five years old, is phenomenal.''

Simon previously said he'd named his diet the Eric Cowell diet after his son, because the youngster loves to munch on raw vegetables.

He said: ''It's like the Eric diet because he actually, apart from ice cream, he actually likes water. I mean, who likes water? And his raw vegetables. So I'm on like, the Eric Cowell diet.''

Simon also admitted that whilst he's yet to allow himself a cheat day, he is frequently tempted by pizza.