Rob Kardashian is looking a little lighter these days and he has more than just a healthy diet to thank. 

The lone brother and son of the Kardashian-Jenner clan has put in the hard work to start slimming down but he's also had the support of his family, especially Khloé Kardashian.

"His mom and sisters are all supportive but Khloé is his number one cheerleader," an insider dished to HollywoodLife. "She’s always pushing him and checking on him and is just so proud of him."

"They spend a lot of time together with their kids [Khloe’s daughter True Thompson, 2, and Rob’s daughter Dream Kardashian, 3] and that’s a huge motivation for him, just being the best dad he can be," the source added.

Considering that the Good American founder has a show, "Revenge Body with Khloé Kardashian," which is dedicated to helping people get in the best shape of their lives, it makes sense that she's on this journey along with Rob. In addition, she's gone through the struggle of losing weight herself. 

 
 
 
 

 
 
 
 
 
 
 
 
 
 
 

A post shared by Rob Kardashian (@robkardashianofficial) on

On June 28, Rob stunned fans when he made some rare posts of himself mingling while attending Khloé's blowout birthday celebration. "Looking good Rob" and "So handsome" comments flooded the comments section of the posts as fans took notice that the 33-year-old had shed some weight. 

"Rob got serious about his health last year and cut out all the junk food and really started making healthy choices with his diet," the source explained. "His weight loss didn’t happen overnight, it’s taken time for him to lose the weight. It’s been close to a year of staying committed to his goal."

"He has his cheat days here and there, but overall he’s eating a very clean low sugar diet and it has really paid off," they shared. 

Rob's success hasn't just been physical, though. Another insider close to the Arthur George sock designer and creator revealed the toll it has had on his mental and emotional well-being too.

"Now that everyone has seen his transformation online, he is very happy and his family is so proud of his weight loss," the unidentified source said. "Rob has really gained a lot more confidence having lost so much weight and getting healthier by the day."

Rob Kardashian & Black Chyna Blac Chyna’s ex Pilot Jones accused her of using him to boost ratings of show with Rob Kardashian. Pictured: Rob and Chyna on her Birthday Celebration And Unveiling Of Her ‘Chymoji’ Emoji Collection at the Hard Rock Cafe on May 10, 2016. Photo: Getty Images/Greg Doherty