Celebrity Shape Shifters

Britney Spears

Britney changes her shape as often as she changes her men. The star who once boasted about doing 500-1000 sit-ups a day, now sports a much rounder frame than those we loved in all her music videos. (GETTY)

Charlize Theron

After gaining more than 10 kgs for her role in Monster and losing it again soon after, the SA export joined the scurry of celebs who’ve all fattened up specifically for movie roles. (GETTY)

Heidi Montag

Heidi’s 2009 plastic surgery overload was met with a flood of criticism. The Hills star underwent 10 procedures in one day and now - obviously - regrets it. What an idiot! (GETTY)

Jennifer Hudson

The soulful singer and actress shed an unbelievable amount of weight after she gave birth last year, shrinking from a voluptuous American size 16 to a 6! (GETTY)

Jessica Simpson

The singer has endured a barrage of name calling and abuse since her super slender days back in 2001. And while her weight continues to rise and fall with every season, Jess insists that she’s happy and comfortable with her curves. This, we like! (GETTY)

Britney is back, but can she compete with Gaga?

Britney Spears

LONDON - AS BRITNEY Spears prepares to launch her seventh studio album Femme Fatale on Tuesday, the pop star faces keen competition from Lady Gaga, Katie Perry and Rihanna, who reign atop Billboard's Hot 100 singles ranking.

Her younger rivals' dominance this week may be coincidental - indeed, Spears also topped the ranking recently with Hold It Against Me. - but the chart is a reminder of how crowded the pop diva market has become since Spears rose to fame as a teenager.

There is little doubt her fans will ensure brisk sales - Spears has sold nearly 70 million albums, according to label Jive Record - and her music is making headlines again instead of personal meltdowns, a custody battle and rehab stints.

Spears kicked off a string of promotions for the album on Friday with a performance at a Las Vegas nightclub. On Sunday in San Francisco she will record a sold-out mini-concert to be aired on ABC's Good Morning America TV show on Tuesday.

Yet after more than 10 years in the music business, Spears, now 29, may have to do more to remain relevant in the era of Gaga, critics say.

'As far as novelty goes, her natural demographic now has an icon as quirky and characterful as Lady Gaga to fascinate and fuss over,' said Andy Gill of Britain's Independent newspaper. 'Gaga's music, let's be frank, is not that much better than, or even different to, that on Femme Fatale, but she knows the lingering appeal of playing dress up,' he added in a two-out-of-five star review of Spears' record. -- REUTERS

Lady Gaga