"Ms. Renee Zellweger has obviously had a lot of different changes occur to her face," Dr. Linder tells ET candidly. "Two of the most dramatic changes for sure are her eyes -- they look very different. The second dramatic change is her jawline. Those are two of her identifying identify features. ... So these have dramatically changed her face with the procedures that she's had."
But what types of procedures does he think she's specifically undergone?
"We don't know for sure, so again this is a hypothesis, but looking at the three different parts of her face -- upper third, lower third and middle third -- it appears that she may have had Botox," he says. "There are no wrinkles in her forehead whatsoever."
But just by judging from the photos alone, it's fair to speculate that the 45-year-old actress has undergone much more invasive procedures.
"Looking at her eyes, they have dramatically changed from her before pictures from just a couple years ago," Dr. Linder observes. "The upper eyelids may have undergone [a procedure] where you remove the skin, and I think it's pretty reasonable that she has had this because the positions of her eyebrows have gone down in her current pictures, and the eyelid crease is more prominent. And if you look at her outer eyebrows, called the lateral brow, they've come down as well. And that's also a telltale sign of having skin removed from the upper lids."
Dr. Linder also speculates that she may have even undergone both a facelift and a necklift.
"Renee's transformation is very, very significant," Dr. Linder says. "It is very likely that she's had several different procedures done."
Check out the video to hear more from Dr. Linder about Renee's shocking new look.