Calvin Harris Raves Over Sam Smith's Impressive Weight Loss: 'He Should Write a Book'

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Sam Smith’s significant weight loss has been well-documented on his Instagram account, and on Wednesday, the 23-year-old singer shared a pic that showed him slimmer than ever.

“California daze,” Smith captioned the pic, in which he posed in a striped shirt and new short-cropped haircut.

WATCH: Sam Smith Is the Skinniest We've Ever Seen Him, Shows Off a Wicked Sunburn

The singer’s new slim physique is so impressive in fact, that Taylor’s Swift’s boyfriend, DJ Calvin Harris, took to Twitter on Friday to compliment his hard work.

“Sam smith weight loss is legendary,” Harris tweeted. “He should write a book big up Sam Smith.”

PICS: Sam Smith Says He Lost More Than 14 Pounds in Two Weeks

Smith has been candid throughout his weight-loss journey, even admitting that hearing someone call him “fat” hurt more than anti-gay slurs.

"If someone called me fat, that affects me way more than someone calling me a f----t," he admitted to Australia’s 60 Minutes last April. "I think just because I've accepted that, if someone calls me a f----t, it's like, I am gay and I'm proud to be gay so there's no issues there. If something calls you fat, that's something I want to change."

WATCH: Sam Smith Admits Someone Calling Him Fat Hurts Him More Than Anti-Gay Slurs