"Rob spends two to three hours a day in a sauna, and weighs himself straight afterwards," the source told Heat. "He's been gloating about how much weight he's losing, but it's mainly water weight—and he never rehydrates, which is terrible for his diabetes."
The insider said that given Rob's weight, "it's dangerous to be sitting in that heat for so long, because it's putting a lot of added pressure on his heart."
Rob, 30, has been looking slimmer recently, according to insiders, but his friends and family are concerned this isn't the best way to do it.
"Rob will do anything to avoid working out, he hates it," the source continued. "He's convinced he's found a shortcut. Rob says he's done the research and he burns more calories and boosts his metabolism by being in the sauna."
And it gets worse! "On top of all that," the source said, "he's also been wearing a sauna suit around the house. He's always red-faced and sweating, even when he's just laying on the couch."
What do you think about Rob's sauna obsession? Has he taken it too far? Let us know in the comments.