Rob Kardashian is battling fat with sister Khloe Kardashian's help as the only son of momager Kris Jenner is reportedly moving into the new Calabasas mansion of Lamar Odom's ex-wife.

"Living alone isolated him. Rob needs to be around people who love him," a source told Us Weekly.

Rob Kardashian would feel at home in Khloe Kardashian's Calabasas mansion, which she purchased from Justin Bieber. And with seven bedrooms and 10,000 square feet of space, he can still be alone in his thoughts but still feel the support of family at the same time.

The sock mogul is also familiar with Khloe Kardashian's habits as he also lived for a time in the mansion she shared with Lamar Odom before they split.

Among all the sisters, Khloe Kardashian was the one who remains supportive of Rob Kardashian as he battles fat, while Kim Kardashian and Kourtney were very critical and momager Kris Jenner was very harsh, according to Star magazine.

After Rob Kardashian's weight gain, Kris Jenner has been reportedly threatening to send him to "fat camp."

"If he expresses an opinion, Kris tells him to be quiet until he starts paying his own way," the Star reported.

The only boy in the Kardashian brood, his depression and the feeling of isolation led to a cycle of destructive habits which only compounded the situation as Rob Kardashian battles fat.

He has been resorting to alcohol, marijuana and Sizzurp, which is a prescription drug syrup.

"Rob has never been in such bad shape - emotionally or physically. Rob was drinking a lot of Sizzurp, and that's one of the reasons he gained so much weight," the source told Star, citing the high sugar content of the syrup.

Because of Rob Kardashian's weight gain, the "Keeping Up with the Kardashians" actor is "well past the point of desperation and now is just flatout miserable."