Simon Cowell has lost half a stone since the start of the year after overhauling his diet.
The 59-year-old reportedly consulted a specialist to test him for food intolerances after he complained of feeling constantly sluggish and run down.
Now thanks to advice from a top nutritionist, the X Factor judge is 7lbs lighter after cutting out refined sugar, gluten and dairy from his diet.
“Simon was feeling a bit run down, so someone suggested he see a specialist about food tolerances,” a source close to the star told the Mirror.
“The specialist revealed he is allergic to a few everyday things which had been making him tired.
“As a result, he has cut out lots from his diet and the impact has been almost immediate. He has loads of energy.”
But that doesn’t mean the music mogul hasn’t found his healthier eating habits a challenge.
The source added, “He’s found it really tough to cut out a lot of things he used to love eating, like sausage rolls.
“But he can’t believe the change it’s had in such a short space of time.
“He’s looking and feeling great at the moment, the best he has in years. He has a real spring in his step, which everyone around him has noticed.”
Simon’s weight loss comes after he vowed to improve his health following a nasty fall in 2017, insisting he wanted to spend more time with his son Eric, five.
Speaking about the fall last year on ITV’s Lorraine, Simon explained it occurred due to his low blood pressure.
He added, “In a weird way it was a wake up call because it wasn’t the end of the world. It was a bit embarrassing…
“I will never hear a bad word about the NHS. It’s like having an MOT, they do every possible test. I was probably overtired, to be honest.
“I feel much better this year, I’m not having so many meetings or late night calls, it’s a bit more of a balance.”