Renee Zellweger debuted an entirely different face Monday night, leaving fans and entertainment industry experts wondering why the “Bridget Jones” star looked so different. A close confidante of Zellweger’s told FOX411 that her drastically different look is a result of the 45-year-old actress’ insecurities.

According to our source, who has been connected to Zellweger since the early days of her career, the changes are hardly a big surprise.

“Insecurities abound,” the source told FOX411. “Hollywood gets to people more than one would like to think.”

In a statement to People.com released early Wednesday morning, Zellweger did not address the rumors of plastic surgery and simply stated her new look was a result of a healthier lifestyle and natural aging.

So which is it, her new life, or same old Hollywood pressures?

“Renee is obviously hyper-fixated on maintaining a youthful appearance; this is likely a result of the interaction between her own personality type and Hollywood’s focus on young females,” observed Harvard sociologist Dr. Hilary Levey Friedman. “The focus on youth and often unattainable perfection, like no wrinkles, certainly can lead those with a proclivity to engage in radical behavior.”

The pressure to stay young is a big issue all around, explained human behavior expert, Patrick Wanis, PhD.

“We the consumers are so obsessed with youth and so hateful to age, and that affects everyone. Hollywood is just serving what we ordered,” he said.

Zellweger hasn’t been seen out in public much since her last project four years ago. She has played the title character in two "Bridget Jones" movies,  and a third film in the series is said to be in the works, but it has hit some road bumps along the way—including issues with the script and Hugh Grant dropping out of the project.

Zellweger recently told E! News she had no knowledge of the status of the third film. "It would be fun," Zellweger said of the idea of doing another installment. But as far the progress of the film, "I have no idea," she insisted. "I'm not being cagey. I just don't know."

Her next film, “The Whole Truth,” is slated to hit theaters in 2015, but her physical transformation now begs the question: Will she still get the big roles that once made her one of Hollywood's most bankable stars?

“Renee Zellweger is a brand she has seriously damaged, or at least changed. She should have thought about careers like Meg Ryan and Jennifer Grey who don’t work as much because they changed how they looked so substantially,” observed Harvard sociologist Dr. Hilary Levey Friedman. “She has chosen a career that puts her in the public eye and for which she is judged based on her appearance.”

If Zellweger is no longer easily recognizable, that's a big problem, Wanis said.

“While people might be reeling from the fact that Renee is not recognizable,  what is more sad is that she has lost all the qualities that endeared her so much and made her so famous – the innocence, the vibrancy and the vulnerability.”

A rep for Zellweger did not immediately respond to a request for comment.

WATCH: Four4Four: Inside Renee Zellweger's change of face