Jen Aniston and Nicole Kidman’s 'Just Go With It' Bikini Bodies Better Than Brooklyn Decker's?

Jen Aniston and Brooklyn Decker. (X17/Columbia)

Adam Sandler’s new romantic, and of course part toilet joke, comedy “Just Go With It” bears all the typical elements for ladies looking for a feel-good love film ahead of Valentine’s Day. And it certainly has plenty of entertaining eye-candy for the fellas that get dragged along to see it.

“Just Go With It” stars three Hollywood beauties all showing off their bikini bodies – Jennifer Aniston, Nicole Kidman, and acting newcomer Brooklyn Decker. But guess what? Pop Tarts saw an advance screening, and Aniston (who turns 42 on Friday) and Kidman, 43, look just as taut, toned and terrific in next to no clothes as their 23-year-old “Sports Illustrated” supermodel counterpart, Brooklyn Decker.

So does this prove that, at least in Tinseltown, being over 40 is no excuse for being out of shape? Is it really that much harder to stay looking fit and fabulous with a few extra years on the resume?

“Age is not an excuse, it’s just a number.  Your health should always be a top priority no matter how old you are,” Tanya Zuckerbrot, MS, RD and author of the popular “F-Factor Diet," told FOX411’s Pop Tarts.

And clearly, the film’s leading male and producer, Adam Sandler, approves of his leading lady’s over-40 physique.

“She (Aniston) manages to be perfect. Aniston’s ankles are even great,” Sandler gushed to FOX411’s Pop Tarts. “Everything about her is pretty darn cute.”

PHOTOS: More pics of Jen Aniston.

Yet Zuckerbrot believes that even without the luxuries that Hollywood actresses like Aniston and Kidman have access to (ie, private yoga teachers, top-notch nutritionists, and airbrushers) the average American woman can also be in fine form post-40.

“You do not have to have the bank account of a Hollywood celebrity in order to achieve an ideal body weight.  The key to successful dieting is to make small changes that will transform your life but not your lifestyle,” Zuckerbrot continued. “A well balanced diet consisting of high fiber carbohydrates, lean proteins, fruits, vegetables and a small amount of heart healthy fats is the key to looking and feeling your best.”

Fitness guru and founder of Exhale’s Core Fusion program, Fred DeVito, concurred that bangin’ bods are achievable for anyone, at any age – but it requires work.

“It does get harder every year to maintain an athletic, fit, slim physique. Our metabolism (which is simply the rate at which your body burns calories) slows down because as we age, we lose lean muscle mass,” he explained. “But you don’t need a personal trainer or chef – the average American can look as lean and fit in their 40's and 50's as they did in their 20's and 30's if they adapt their lifestyle and habits to counter act the effects of a slower metabolism. Don’t waste an hour doing only cardio! Do strength training exercises to build lean muscle mass.  Muscles are the engines of the body and when they are strong and dense, your body becomes a fat burning furnace, not just for one hour, but 24 hours a day.  Even when you are sleeping!”

Okay, stop yelling! Trainers....

However, Los Angeles-based pop culture expert and television host Carrie Keagan begs to differ that average folks can ever keep up with the likes of Aniston and Kidman.

“There is definitely a phenomenon in Hollywood recently where women over 40 look like they haven't aged a day since their 20's.  With the availability of such modern marvels as personal trainers, nutritionists, plastic surgeons, dermatologists and makeup artists, it's no wonder! Celebs have access to products and procedures that regular people don't, and at A-list levels these things can cost as much as the average persons house,” Keagan told us. “But before we go hating on them for having it all, let's just remember one thing – it is their job to look good! They work really hard at it, and we wouldn't accept our celebs any other way.”

On a side note, many were surprised to learn that Oscar-winning actress Nicole Kidman is even in the Sandler-banter flick, where she plays the role of Aniston’s over-the-top college nemesis, Devlin. Sony publicity left her off the main movie poster, which instead features Aniston and Sandler, along with a rear view of Decker in the background. And although Kidman acknowledged that she’s no comedienne thus the role is “very unusual” for her, she actually steals the show and is perhaps the funniest of them all.

“Kidman was great! So was Dave Matthews (who plays her husband in the film.) You can't ruin that genuine ‘what the…?’ moment by putting them on the poster,” Keagan added. ‘The element of discovery is so much cooler! I think Adam Sandler likes to surprise people with the characters in his films. ‘Just Go With It’ is no exception!”