The reclusive reality star was spotted out in Los Angeles with girlfriend Blac Chyna on Tuesday, following a gym session.
Kardashian, 28, was dressed in all black and a LA Dodgers cap as he was getting dropped off by Chyna, 27.
Kourtney, Kim and Khloé's younger brother was diagnosed with diabetes in late December after battling depression and struggling with his 100 lbs. weight gain.
But as of late, Kardashian has been documenting his determination to workout. On Monday, the sock designer shared a photo that read "Progress = Happiness" on Instagram, days after posting several throwback pictures of himself when was slender.
Since linking up with Blac Chyna last month, Kardashian has showed off his gym sessions on social media as well as his diet regimen.
The mother of one took to Snapchat on Monday night to document their dinner date together, during which she cooked him seared meat and steamed vegetables.
Kardashian's brother-in-law Kanye West also vocalized Rob's weight loss in his song "Highlights" off new album, The Life of Pablo, in which West raps, "Blac Chyna f---ing Rob, helped him with the weight."
Love appears to be the best motivator for Kardashian to lose weight.
"Rob has fallen hard for Blac Chyna. She makes him super happy and this is the first time that he's felt so optimistic about life in years," a source told PEOPLE. "For the first time in forever, Rob seems very excited about the future."