Alongside a throwback photo of the couple in February, showing Kardashian at his heaviest, the famous sibling to Kim Kardashian, Khloe Kardashian and Kourtney Kardashian said he was "focused and determined' to keep going.
"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," he wrote. "Happy I found my motivation."
Earlier this month, the 29-year-old Keeping Up With The Kardashians personality revealed he and Blac Chyna -- born Angela White -- were engaged.
The 27-year-old model celebrated her engagement opposite longtime friend and fellow model Amber Rose in Atlantic City over the weekend. The celebrity shared several photos of the festivities on Instagram.
Chyna and Kardashian became publicly linked in January, soon after the famous family member was hospitalized and diagnosed with diabetes.