The reality star was seen trying on noticeably smaller sizes of clothing on Friday in a video filmed by girlfriend Blac Chyna.
"Hi babe," Chyna, 27, said to Kardashian, 28, who modeled a slimming gray ensemble.
The mother of one has been helping her boyfriend get fit by cooking healthy meals and improving his diet.
In addition, Kardashian has been exercising more after spending two years out of the spotlight due to depression and a 100 lbs. weight gain.
Most recently, the couple, who have been dating since January, enjoyed a protein-packed BBQ dinner with the sock designer going shirtless.