Lately, it seems the trend in movie-producing is to take an old concept or entire film, “make it better” and present it to the masses like diet cola. You think you like it because it’s still brown and carbonated, but in reality, it’s nothing like the real deal. Jennifer Garner stars in “13 Going on 30,” a throw-back to 1988 and Tom Hanks’ “Big” — only without the calories.

Garner plays Jenna Rink, and at the movie’s beginning is a frustrated 12-year-old (played by Christina B. Allen). Jenna wishes, like most 13-year-olds, that she could be one of the most popular girls in school — at the expense of everything. And on the day of her 13th birthday, she invites all the popular kids to her birthday party. The food chain of junior high pulls through, and she is ditched by the cool kids and left with her best friend Matt. After taking her anger out on Matt, she wishes that she were 30 — and magically, her wish comes true (fairy dust included.)

It’s ironic Jennifer Garner’s first “big kid role” in film is playing a 13-year-old, and at least last year’s flop “Daredevil” had her doing cool kung-fu moves. All things aside, she did pretty well playing a wide-eyed young girl, but writers Cathy Yuspa and Jon Goldsmith fail trying to out-do the “magic” they created in 2000’s “What Women Want,” starring Mel Gibson.

A few good notes can be hit when talking about the chemistry between the leads. Jenna wakes up as a successful magazine editor in New York, and many awkward scenes later, tries to find her friend Matt (played by Mark Ruffalo). Ruffalo is absolutely charming as modest, grown-up Matt.

A conflict happens at work, and Jenna calls on the assistance of Matt. Putting aside the rejection he felt from her when they were growing up — which she obviously doesn’t remember — Matt decides to help. When Jenna has a clich‚ “epiphany” that she loves Matt, the sparks between them are somewhat realistic. This creates the same facade as diet pop, and you find yourself wanting things to work out for Jenna and Matt.

Another honorable mention goes to Judy Greer in her role as Jenna’s coworker and best friend. Greer has previously held mostly wishy-washy roles in films like 1999’s dark comedy “Jawbreaker.” In “13 Going on 30,” Greer performs well as snotty, conniving Lucy and provides a strong contrast to Jenna’s sweet demeanor. However, Yuspa and Goldsmith’s script indulges in the stereotype that all career women are scheming and evil. And this isn’t exclusive to Lucy — they wrote it into the type of conduct that grown-up Jenna was involved in before she got in touch with her “inner child.”

“13 Going on 30” is a novelty film. You still have the same reaction you get when you see something cute, but upon further contemplation realize that the calories are really worth it — and you decide to relive the real deal and rent “Big.”