Nick Jonas Explains His Viral Shirtless Selfie

To say the Internet went collectively nuts when Nick Jonas posted this photo of his banging new physique on Instagram is an understatement.

The 20-year-old singer surprised plenty of people -- Jonas Brother fans and non-fans alike -- when he showed everyone just what he's been hiding underneath his shirt, and he recently chatted with Ryan Seacrest to discuss the amazing reaction he's been getting.

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"It's been a pretty hilarious reaction," he said during an interview on On Air with Ryan Seacrest Thursday. "There's a lot of people running around without their shirts on these days, so I just didn't want to add to the noise, but I felt like as a diabetic … it's twice as hard for us diabetics to stay in shape. I've met a lot of diabetics recently who have come to me and said, 'Thank you for being so vocal about fitness and health' because it's helping them. I just wanted to give some inspiration to those people."

Though he admitted that that's not all he's been hitting the gym for -- he also has some pretty steamy love scenes with Transformers: Revenge of the Fallen actress Isabel Lucas in the upcoming film Careful What You Wish For.

"I wanted to look OK," he said bluntly.

As for those wondering if it's really him taking the shirtless pic, Nick confirms that it is-- and that it only took him one take for the perfect photo.

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"I'm not lying here … it was one picture ... There's a self-timer setting on the camera. I debated [posting] it with my brothers and people in our band. I was like, 'Should I do this?' and they were like, 'You have to!' So I did it."

Just don't expect any more shirtless pics anytime soon.

"I don't know if it's something I'd do again," he said. "People will just have to go see the movie for more of that."