Nick Jonas tweets shirtless selfie

On the same day that 44-year-old "Wolverine" star Hugh Jackman tweeted a photo of himself dead-lifting more than 400 pounds, Nick Jonas showed off his pecs and abs in a half-naked Instagram photo.

"I never do this, but..." the 20-year-old Jonas Brother said. "Healthy living and fitness update. Post workout picture. #diabeticinshape #2.0."

Jonas was diagnosed with Type 1 diabetes at age 13. The active pop singer said two years ago that diabetes inspired him to eat health and stay in shape.

I’ve always been really athletic and active, but today, it’s really just working towards making sure that every part of my goal to keep my diabetes in check is there -- from things like how I eat to how much time I spend in the gym or in a chair in the studio. The smallest things, like sitting in a chair in the studio all day, will cause my blood sugar to spike -- it will just go high -- so I have to be active in some way. So I go in the live room, play drums for a while, come back, and it’s all good.