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  (Photo: Reuters/Carlo Allegri)
  Singer Kelly Clarkson performs at the Z100's Jingle Ball concert at Madison Square Garden in New York December 9, 2011.

Often criticized for her weight, Kelly Clarkson has debuted a slimmed-down figure Sunday night at the Billboard Music Awards.

Wearing a pink gown with a plunging neckline, Clarkson took the stage to perform her new single "Dark Side." The "American Idol" winner received frenzied applause for the number.

The singer's fluctuating weight has been speculated in the media since her days on "American Idol" in 2002. Within minutes of her performance at the Billboard Awards, fans took to online resources such as Twitter posting about Clarkson's trim figure as well as her voice at the event.

"I think I'm a closet @Kelly_Clarkson fan," wrote Jurnee. "She looks gorg! Sounds great too @billboard #bbma"

Cambio posted, "Kelly Clarkson looked and sounded amazing at the Billboard Music Awards," before asking how much weight the star has lost.

Twitter user Chaci posted, "Anyone address that @Kelly_Clarkson sounded & Looked amazing tonight, oh and she sang live too!"

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"omg," wrote Lawson. "Kelly Clarkson's performance was amazing @ the Billboard Music Awards. World Class Performance!"

Damian boasted, "Kelly clarkson looks utterly phenomenal at the billboard awards."

"She looks great and sounded amazing," wrote Facebook user Nancy. "This girl can sing!"

Clarkson's previously-released single "Stronger (What Doesn't Kill You)" remains the week's most-played song from an "Idol" alum.

Just two months ago, reports revealed that Clarkson was romantically involved with Brandon Blackstock- the son of her manager Narvel Blackstock, and the stepson of Reba McEntire.

"Before Brandon, Kelly had a really tough time with love," said a source close to the 30-year-old, according to Us Weekly. "[Brandon] is just what she needed."

The "A Moment Like This" singer has a very busy schedule ahead with NBC's new television series "Duets" kicking off this week. The show sees Clarkson alongside John Legend, Robin Thicke, and Lionel Richie, among others.