07/30/2013 at 04:55 PM EDT
Looks like another Disney star is all grown up!
, 20, Instagrammed
an abs-baring "post workout picture," he explained of an image he posted on Tuesday.
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."
Unexpected celebrity selfies are apparently in the air. Jonas's revealing photo comes just a week and a half after Geraldo Rivera, 70, Tweeted – and deleted – a shirtless shot of himself
fresh out of the shower.