“Keeping Up With the Kardashians” star Rob Kardashian vowed to lose “pregnancy” weight with fiancée Blac Chyna on an Instagram post Tuesday. The former recluse ballooned to over 275 pounds, a much huskier frame than when “KUWTK” started in 2007.

The failed Arthur George sock designer posted a side-by-side image of him and Chyna. Kardashian, 28, posed to the side in a white tank top, while his future wife rocked a string bikini in her pre-pregnancy body.

“Oh yeah we snapping back lol,” he wrote to his 7.3 million followers. “Baby will be here in 4 weeks and I'm done with carrying this pregnancy weight. Me and my baby gonna be righttttttt ,,, MOTIVATION TIME‼ We almost there Chy.”

He added: “Chy looks so bomb here aghhhh” The post garnered nearly 130,000 likes and thousands of comments.

Even though he’s gearing up to be a first-time father, Kardashian isn’t nervous. “Rob is fine. He says he's really fine and calm about it, but I was like, ‘It's OK if you're nervous!’” sister Khloé Kardashian told Us Weekly at the launch of her Good American denim line Tuesday. “I think anybody would be nervous. But he seems super chill about it, so that's good.”

Khloé Kardashian, 32, is excited to be an aunt for the sixth time. Chyna, 29, plans to include Khloé in the baby’s life as much as possible. Her future sister-in-law joked the baby is as much Khloé’s as hers.

“Chyna keeps joking like, ‘This is our baby!’ Like with me too,” the reality star explained. “So it's like, I haven't been getting prepared, but I'm like, ‘Should I be putting a nursery in my house too?’ Chyna's like, ‘Are you so excited? We're having a baby soon!’ And I'm like, ‘Wait, are you kidding or am I really having a baby with you?’”

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