EXCLUSIVE: How Renée Zellweger's Brutal 4,000-Calorie-a-Day Diet to Plump Up For Original 'Bridget Jones' Movie Plunged Actress Into Panic Attacks

Renée Zellweger and her boyfriend Ant Anstead held hands as they left the London after-party for Peacock's Bridget Jones: Mad About the Boy on Jan. 29, looking happier than ever.

But RadarOnline.com can reveal the movie franchise is a source of bad memories for the actress – including how she had to eat an unbelievable amount of calories to pile on pounds for the first flick in the rom-com series.

And in a rare move for the private star, the couple were joined by Anstead's older children, Amelie. 20, Archie, 18, and his parents, Nigel and Sue.

Ant also has a 5-year-old son, Hudson, with second wife, Christina Haack.

Sharing the joyful moment with her partner of three years and his family felt like a scene straight out of Bridget Jones, but this was real life.

"She was thrilled to have Ant join her at the premiere and show him off," an insider told us. "It goes to show how comfortable she is with this relationship."

Two-time Oscar winner Zellweger, 55, is back in the spotlight for the fourth installment in the Bridget Jones film series.

The beloved British character so convincingly played by the actress since 2001 has brought her lasting fame but also led to intense scrutiny of everything from her weight to her romantic life.

Now Zellweger is opening up about her biggest regrets, why she ditched Hollywood for six years and a terrifying health scare.

At the time of taking the Bridget Jones role, the star was America's sweetheart, all dimples and toothy smiles, who Tom Cruise had "at hello" in the 1996 classic Jerry Maguire.

Zellweger has appeared in nearly 50 films and prestige TV series – and has had her share of high-profile romances, from Jim Carrey and Jack White to Bradley Cooper, as well as an ill-fated marriage to country star Kenny Chesney in 2005, which was annulled due to "fraud."

In a recent interview. she admitted she has previously felt like she has lost herself, telling The Guardian newspaper she'd advise her younger self: "Girl, slow down."

She added she was "moving from place to place" amid her stardom – saying she was "constantly living" of a suitcase and "never unpacked" until she was aged around 41.

And in 2010, when the actress was facing bad reviews, she decided to step back from her career.

She told Vogue: "I needed to. I was sick of the sound of my own voice. When I was working, I was like, ‘Oh, my gosh, listen to you. Are you sad again, Renée? Oh, is this your mad voice?’ It was a regurgitation of the same emotional experiences."

Our insider said about her time away from the spotlight: “A lot of people told her she was making a mistake. But it was more important to Renée to get in a healthy frame of mind and live at normal life outside of the Hollywood spotlight.

"During her time away, she explored new passions – writing music, studying international law, building a house, rescuing two dogs and cherishing time with family and a close friend facing health struggles.

Zellweger has also faced major health issues.

Over the years, the naturally slim star repeatedly gained and lost up to 30lbs to bring Bridget Jones to life.

But the constant fluctuations in her weight and the 4,000-calorie-per-day diet she was on to bulk up for the part took their toll, leaving the A-lister feeling "mentally whacked" and "all over the place" while filming Bridget Jones's Diary in 2001 and its sequel Bridget Jones: The Edge of Reason three years later.

She said: "I had a panic attack with all the specialists talking about how bad this is for you long term putting on that much weight so quickly.

"They were all saying, 'You must stop this now, or you're going to die.'"

She's since said she won't gain or lose weight for a role.

After enduring scrutiny over her weight, relationships and career choices, Zellweger chose to prioritize herself and sources say she's more selective about projects – winning her second Oscar for 2019's Judy.

By the time the actress met Anstead, 45, on the set of his show Celebrity IOU: Joyride, she felt whole again.

"She's found balance in her life she works when she wants to and has plenty of other things to keep her fulfilled when she doesn't," said our insider.

The actress, who affectionately calls Ant "my fella," has said she stays off social media and lives in the present.

Our insider added: "Everything is going so well for Renée."