Rob Kardashian Appears Thinner at Kim Kardashian’s Birthday Party in Rare Video

Eric Todisco

Rob Kardashian looks to have lost weight in footage from his sister Kim Kardashian West‘s low-key birthday celebration on Monday night.

In a video that Kim, 39, shared to her Instagram story, a man who appears to be a leaner Rob, 32, is seen in a black shirt and shorts walking through her house. His face is not shown.

Towing behind Rob were Kim’s daughter Chicago, 21 months, and Kourtney Kardashian‘s daughter Penelope, 7. The KKW Beauty mogul wrote on the video, “I love my family.”

And in a video posted to Khloé Kardashian‘s Instagram Story from the gathering, someone who sounds like sister Kylie Jenner can be heard exclaiming, “Robert! Robert!”

Rob  — who is dad to daughter Dream Renée, 2½, with ex Blac Chyna — has struggled with weight issues over the years. But in June, he revealed on social media that he was back at the gym for his first day of a new fitness regimen.

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Kim Kardashian/ Instagram

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In the photo he shared from inside the gym, Rob was surrounded by ropes, a weight bench and multiple resistance machines. A basketball hoop could be seen outside the facility’s open sliding glass doors.

“Day 1 all good,” he wrote, adding strong-arm, pregnant woman and Vulcan salute emojis.

In June 2018, a source told PEOPLE that Rob “can’t seem to get healthy even though he says he wants to be” and is “constantly up and down” in his weight journey.

The insider noted that he did lose “some weight” after his 2017 breakup with Chyna. “Things were looking good for him,” said the source. “But then drama comes into his life or he goes through tough times and he gives up.”

And the source said he struggled to maintain a healthy diet: “Food is the hardest part for him. He’s a big comfort eater.”

Although he was once a fixture on his family’s reality show, Rob retreated from the Keeping Up with the Kardashian cameras, telling PEOPLE in 2016, “I gained a bunch of weight and was super uncomfortable in my skin. The whole weight thing really affected me.”

Gabe Ginsberg/Getty

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Rob Kardashian/Twitter

Despite his bumps in the road, an insider told PEOPLE in March 2018 that, at the time, Rob was “eating better and has a trainer” and felt motivated to “stay healthy for his daughter’s sake.”

“He’s focused on what he should be focused on: Dream and his health,” the source added. “He wants to stay healthy for his daughter’s sake. Dream was a huge wake-up call for Rob. He wants to be the best dad possible.”