Cheryl Burke dished the details of Rob Kardashian's weight loss on Dancing With the Stars this week to Burke wrote an article for the magazine published Monday where she expressed how proud she is of him.

Rob did a great job last week on 'Dancing with the Stars,' Burke wrote. He was really feeling the dance. I think it gave him some confidence with the judges. And he was really happy, especially when Carrie Ann told him he was better than his sister. It's just nice to hear positive feedback, especially for Rob. He does have his insecurities and he does have low self-confidence. I think it really pushed him to do even better this week.

Burke added that Kardashian has become more competitive.

No one wants to get a bad score on Monday night, and the only way to avoid that is to really work hard, she wrote. He's taken it seriously from the beginning, but I think now he wants to make sure he improves every week.

When it comes to Kardashian's physique Burke said it has changed a lot.

He's lost a lot of weight, she wrote. His whole physical appearance has changed. He's using different muscles. He's super sore all the time. I'm not sure if he's changing his diet, but the cardio is really good. I think he lost most of the weight just rehearsing from the jive because it's so fast-paced.

Overall, Burke said Kardashian is now feeling more comfortable with his body.

He's starting to wear tank tops to rehearsals. And you'll see his arms out, she wrote for In the beginning, you'd never see that. He looks at himself in the mirror. It's really cute.