Rob Kardashian has lost 50lb

London, Apr 13 (PTI) Reality TV star Rob Kardashian has lost 50lbs but wants to lose another 50 by next month.

The sock designer currently weighs 248.4lbs, down from his heaviest weight of 298lbs, but wants to lose another 50lbs before his fiancee Blac Chyna's birthday in May, reported Female First.

"Looking from where I started 298lbs to my current weight now 248.4lbs. I'm focused and determined to reach my goal weight 200-205lbs .... Happy I found my motivation," he wrote on Instagram.

It is believed his motivation is his fianc e, who he recently proposed to after a whirlwind romance.

Last week Blac, 27, revealed she was planning to get Rob in shape by her 28th birthday on May 11.

Rob, 29, has battled for his weight for some time and contracted diabetes, and his sister Khloe Kardashian revealed last month he has been working on his fitness.