Nick Jonas left little to the imagination on Tuesday when he posed a shirtless selfie.

The musician, 20, Instagrammed an abs-baring "post workout picture," he explained of an image he posted.

Posing with his right arm lifted behind his head, the toned musician stood with a serious look on his face, while wearing his Nike fitness shorts very low on his waist.

"I never do this but ... Healthy living and fitness update," he wrote. "#diabeticinshape #2.0."

At the age of 13, Nick was diagnosed with Type 1 diabetes. Since then, he majorly cut back on his sugar intake and stays away from regular soda.

"When I wake up, the first thing I do is check my blood sugar, see where I am," Nick explained to Good Housekeeping in 2011 about what a typical day for him is like.

"Then, I usually eat breakfast, typically an omelet because it has eggs, which are good, and other things that help me stay stable," he added.

After the diagnosis, Nick's mom Denise admits she was scared for her son.

"I was terrified that diabetes might ruin Nick’s life. I thought that his being diagnosed would completely stop all the progress that he had made so far. I thought all his hopes and dreams would be completely devastated by it, and it might stop him from touring and performing and doing what he loves. But he proved me wrong," she said. "Taking the time to be educated was a big factor for both of us, and for our family. We started learning as much as we could, to help him manage his condition."

His brother Kevin Jonas also weighed in on the diagnosis at the time.

"Well, obviously we've seen that you can live your dreams and do what you want while still dealing with a chronic illness," Kevin said. "I believe that's possible when you rely on other people, like your family."

Tags: Nick Jonas Jonas Brothers