Christina Aguilera's weight gain is the only thing fans noticed after her amazing performance at the Michael Jackson Tribute concert Saturday, Oct. 8.

The 30-year-old pop singer performed "Dirty Diana" and "Smile" at the event, called "Michael Forever." Her act was met with rave reviews, but her "super skimpy outfit," which some felt made her look fat, was what got press tongues wagging.

The singer's weight has fluctuated over her years as a pop icon, and after her divorce from music producer Jordan Bratman in October 2010, she has been sporting a noticeably fuller figure. Over the last few months, Aguilera slimmed down again, earning nods for the weight loss.

Following her Saturday performance, however, Internet bloggers, commenters and publications all ripped into the singer, criticizing her choice to wear a leotard and fishnet tights with her "very curvy figure."

Kelly Osbourne, commenting on the performance, went even further, slamming Aguilera after she claims the petite star mocked her for her own weight gain.

"[Christina] called me fat for so many f---ing years," reality-star Osbourne said of the fellow 5 foot 2 inch celebrity. "F--- you, you're fat, too," she went on, recorded on E!'s Fashion Police show. "Maybe she is just becoming the fat b---h she was born to be."

Many tabloids have been careful to say that Aguilera's weight gain "hardly makes her fat." But if that's the case, why is her weight gain, reportedly no more than 15 pounds, causing such a stir? Buzzfeed has posted an article of the "Top 5 Most Frightening Pictures of Christina Aguilera," and comments on Twitter and Facebook run the gamut from "she's a real person, get over it" to "that fat chick ate christina aguilera!"

What do you think? Does Christina need to lose weight? Or should critics lay off her new curvy figure?

Christina in the infamous leotard-fishnet combo. Sites called her look "disheveled" and her outfit "unflattering."

Christina Aguilera, 2001

The release of Aguilera's fourth studio album, "Stripped," was accompanied by a slew of comments on Aguilera's spray tan, her 'skanky' look, and her (moderate) weight gain. The star quickly slimmed down.

Christina seemed the perfect balance of toned and curvy on her "Back to Basics" tour.

Here, Aguilera wears an outfit very similar to the one she sported at the Michael Jackson Tribute concert.

Following her divorce from Jordan Bratman, Christina gained a noticeable amount of weight, a fact that was noted (and lampooned) by various media outlets.

Christina made a comeback with the hit reality show, and was frequently met with adoring looks and stammering compliments by her male fans on the show.

What do you think? Is Christina too heavy? Or should the paparazzi lay off?