Rob Kardashian suffers massive weight loss, pictured at Khloe Kardashian birthday party

Fans were surprised to see Rob Kardashian looking trimmed at his sister's birthday party.

Over the weekend, Khloe Kardashian clocked 36 years.

Photo of Rob posing with his elder sister Kourtney Kardashian at the party.

If you recall that Rob Kardashian skipped sister Kim Kardashian and Kanye West’s 2014 wedding after feeling uncomfortable in front of photographers covering the event.

“I was doing my suit fittings in Paris right before the wedding and I just wasn’t comfortable. I’m 6’1″ and at my most, I probably weighed 300 lbs," he told People.com.

He continued, “There were cameras at the airport on our trip there and I was very unhappy with the person I saw in all the pictures. I’m upset I missed my sister’s wedding but it was a personal decision.”

According to reports, Rob has been hitting the treadmill