Oasis, Robbie Williams and a string of famous brands spent years fruitlessly trying to crack America. For wellness author Amelia Freer, all it took was one Instagram post from UK soul sensation Sam Smith.

In perhaps the starkest example yet of the power celebrity social media endorsements can have on a brand’s fortunes, Smith has catapulted Freer’s book Eat. Nourish. Glow. to the top of bestseller lists. Harper Collins had no plans to publish the book in the US, but after Smith’s plug attracted 150,000 likes on Instagram, the company rapidly scrambled the book into print, according to The Wrap.

The 22-year-old chart topping singer has hit headlines in recent weeks thanks to his dramatic weight loss, which Smith credited to Freer’s clean home-cooking philosophy.

In an Instagram post, Smith wrote: “Three weeks ago I met a woman who has completely changed my life. Amelia Freer has helped me lose over a stone in 2 weeks and has completely transformed my relationship with food. Everyone go check out her incredible book, and start to live healthy.”

Eat. Nourish. Glow. has swiftly become a bestseller, with nutritional therapist Freer conducting countless media slots in support of the book, which has won praise from celebrities including Smith, James Corden and Boy George.

The book sees Freer explain her 10 steps for losing weight, looking younger and feeling healthier, placing an emphasis on healthy additive-free home cooking, with the inclusion of 25 recipe suggestions.

“I am beyond thrilled to learn that my book is number one on Amazon and iBooks in the UK – and also hit the top spot on Amazon in the US,” wrote Freer in her own Instagram post.

“I am having to pinch myself. It was a dream come true for me to just write a book but for it to be so well received is utterly humbling. Above all, it’s awesome that Nutritional Therapy is getting the attention it deserves and that Eat. Nourish. Glow. is impacting so many peoples lives and spreading health! This is beyond anything I could ever have wished for. x”