Cheryl Burke: Rob Kardashian has lost a lot of weight on 'DWTS'

Cheryl Burke has opened up in the past about her body issues, but the "Dancing With The Stars" professional claims her season 13 partner Rob Kardashian is coming to terms with his after losing "a lot of weight."

"He's lost a lot of weight. His whole physical appearance has changed. He's using different muscles. He's super sore all the time," Burke wrote in People magazine, where she moonlights as a blogger. "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."

The 24-year-old television personality, and brother to reality star Kim, and Burke, a 27-year-old two-time champion, received 24 out of 30 from the judges for their FoxTrot on the third week of ABC's hit celebrity ballroom dancing series on Monday (read recap). The pair's scores placed them in the middle of the scoreboard, similar to last week.

"I can tell Rob is getting more comfortable with his body because he's starting to wear tank tops to rehearsals. And you'll see his arms out. In the beginning, you'd never see that. He looks at himself in the mirror. It's really cute."

"She obviously, every week, makes me feel comfortable out there," Kardashian told OnTheRedCarpet.com on Monday. "I'm not, like, counting the steps. I just feel great, comfortable, not nervous. I'm hoping it stays that way and that pattern continues. I know it's going to get harder and harder and harder."

Burke's past partners include NFL player Chad Ochocinco, wrestling star Chris Jericho and singer Wayne Newton. She won the competition with 98 Degrees member Drew Lachey in season 2 and again with retired football star Emmitt Smith in season 3.

Earlier in the year, Burke opened up about her weight struggles and said she was still upset about tabloids calling her fat in July 2008.

At the time the photos were published, Burke said, "You don't have to be anorexic to be beautiful." But now she has admit that she was devastated and tried everything to drop the weight, from starvation to diet pills.

But thanks to Burke's dancing schedule and a focus on eating healthy, she gradually dropped the weight, but left room for some splurges.

"I'm not going to deprive myself, but instead of eating potato chips I'll eat Triscuits or low-fat Cheez-Its," Burke told People magazine in January. "There are moments when I'm like, 'Ugh, the camera adds 10 lbs... but as long as I work up a sweat and eat clean, I'm okay. I feel great about my body."