Which Teen Mom Boyfriend Is Bulking Up? (PHOTO)

He be up and the gym just workin' on his fitness! A slender dude by nature, this Teen Mom boyfriend had trouble bulking up in the past, but a little hard work goes long way — something he must have learned from his fit and fabulous leading lady.

Our mystery man has dreams of becoming a famous actor, and if this photo is any indication, he's on the fast track to success.

Can you guess his identity? Click through to the next slide for the reveal.