Famed workout expert Susan Powter took to YouTube to warn Gabourey Sidibe about her weight, in a rant that expressed her concern for the actress.

"Let me tell you something, Gabby, because Gabby's the only one who matters here, your weight is going to affect everything in your life -- from every breath you take, because a human body carrying that much fat is under the burden," she explains in her video.

"Your weight, child, is going to affect every moment of your day, certainly your career. You are in an industry where you're going to be judged microscopically," the 'Stop the Insanity' guru adds. Watch It: