What The Heck Is Diet Rock?

Check it: my boys Nickelback just released a video for their new song "Edge of a Revolution." The video is good: very glossy, you can tell it cost some cash. No big deal since the guys in Nickelback are loaded. Plus they are a hit machine. Anyway, I was reading Blabbermouth comments about the video (I know, I know) and people kept calling them "bro rock"and "diet rock" I have never heard the phrase diet rock... ever. What does that even mean? Someone please enlighten me.

Nickelback will release their new album, No Fixed Address, on November 18. They plan to tour in 2015 -- and I'll totally be in the crowd at one of their shows.