After being told his weight gain could eventually threaten his life, Rob Kardashian has been working with a trainer and has finally "turned his life around," a source tells ET.

"Rob has struggled nonstop for years with his weight and he finally seems to have turned his life around," the source says. "Lately Rob's friends have been talking about how proud they are of him because he made his health a priority."

"He was warned that if he didn't lose weight, it could eventually become life or death, but since then he lost pounds and feels so much better," the source continues. "He works out regularly with a trainer and that has made a difference in his shape. He really is beginning to look like the old Rob."G