After being scrutinized for gaining a little weight over the years, Christina Aguilera shed the pounds in 2013.

The 32-year-old showed off her slimmer figure when she performed at the Billboard Music Awards in May. The singer wore a black dress as she hit the stage with Pitbull for their song Feel This Moment.

A few days before the award show aired, the singer also posted a photo of her thinner self on Twitter looking stunning in a black bra and skirt. She captioned the image, "On set shooting music video with @Alexoficial for #HoyTengoGanasDeTi."

The star, whose career began 15 years ago, has often been criticized for her weight fluctuation.

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"I've been through my highs; I've been through my lows. Being too thin, being bigger. I've been criticized for being on both sides of the scale. It's a noise I block out. I love my body. My boyfriend loves my body. My son is healthy and happy, so that's all that matters to me," she told Marie Claire in January 2012.

In regards to her weight loss, a source told Us Weekly in June, "It's more of a mind-body thing for her. She believes in exercise that she enjoys, doing strength work as opposed to intense cardio."

In March, another source also told People that Aguilera has begun eating healthier and working out on a regular basis. The singer has been training with Tee Sorge, who also helped her shed some pounds for her 2010 role in Burlesque.

Scroll through our gallery to see photos of Aguilera before and after her weight loss.