Kim Kardashian's little brother has been absent from family activities as of late – and was not part of the clan's trip to Thailand.
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The reality TV star is said to be depressed over his weight gain.
His activity on social media has also been minimal until these last few days, and he appears to have closed and re-oped his Twitter and Instagram accounts.
Rob is reportedly struggling with body image issues after gaining weight – and has apparently headed off to a fitness camp in an effort to lose the extra pounds.
Last week Kris Jenner was spotted boarding a plane with the 27-year-old who was said to be heading off to attend a weight loss program.
The 'Momager' is said to have urged Rob to lose 70lbs ahead of big sister Kim's wedding to Kanye, reportedly set to take place in May.
no one will ever understand how much it hurts— Robert Kardashian (@robkardashian) abril 1, 2014
He has been open about his struggles with his weight – openly talking about it during series nine of Keeping Up With The Kardashians.
In a recent episode he confessed: "I've been the most unhappiest person for about a year and a half and it's very, very easy to fall off the wagon. I need to literally dedicate my entire life to my fitness."
The catalyst for his problems is said to be his split with Rita Ora in 2012, after which he gained 60lbs.
Presumably then, Rita's comments this week that Calvin Harris, whom she dated after Rob, was her first love, won't have helped his mood.
Rita told Elle magazine of Calvin: "He got something out of me that I never thought I had. Yes, like falling in love. I just didn’t think I had it. I’d never experienced it before. And I was just like in the wilderness, thinking, 'Will it ever happen?'."
Rob is said to have also found the breakdown of sister Khloé's marriage with his close friend Lamar Odom difficult to come to terms with as well as his mother's separation from Bruce Jenner – the man who has been his stepdad for 22 years.