Rob Kardashian and Blac Chyna have recently announced their engagement, and it would seem that the bride-to-be has wasted no time whipping her man into shape. The couple that sweats together, stays together?  

Rob Instagrammed the above picture of the couple and said he's lost fifty pounds so far, and has about fifty more pounds to lose in order to reach his goal weight. Way to go, Rob, fifty pounds is like one whole Kardashian butt cheek!

Sources: Perez Hilton