His fans took to social media recently fearing the 23-year-old had gone too far with his radical weight loss.
But the Stay With Me singer says he’s never felt better – or happier – since losing more than 20kg.
Newly single Sam says the secret is simply developing a better relationship with food with the help of British nutritionist Amelia Freer.
Sam, who is quick to stress he’s not paid to endorse Amelia, first showed the results of a new lifestyle on his Instagram acocunt in March 2015.
He was snapped posing with Amelia and holding her new book, Eat, Nourish, Glow.
“Three weeks ago I met a woman who has completely changed my life,” he wrote alongside.
“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. It’s not even about weight loss it’s about feeling happy in yourself.
“Love you Amelia & thank you for making me feel so happy inside and out.”
Sam later admitted that picking the right foods would be a “battle for the rest of his life”, but now feels that Amelia has given him the tools to make better choices.
Amelia’s book focuses on a gluten-free Paleo-style diet, which includes high-quality animal proteins, non-starchy vegetables, legumes, and health fats.
Some foods that are encouraged are organic foods such as eggs, free-range chicken and vegetables. The diet restricts processed foods, sugar, grains, alcohol and dairy.
According to Amelia, her eating principles are about having a better food philosophy and relationship with food and not entirely about weight loss.
In an interview with the Telegraph, Amelia explains that dieting is not simply about “eating less and moving more” as there are other factors to consider.
She adds that most diet plans are a “one-size-fits-all” type of approach which shouldn’t be the case since everybody is unique.
“Our bodies are inherently different not just by age, sleep quality, physical activity and hormones but by other factors as well.
She explains that a healthy diet for a healthy body should be a long-term habit and not just a short-term solution.
Amelia has also worked with Boy George and James Corden, who also credit her for their weight loss success.