She claims she has dropped two dress sizes after splitting from her boyfriend Seb Chew.

But sources say the real reason behind Lily Allen's recent weight loss: she is paranoid over her "chunky" thighs, ankles and rear and has been mortified by magazine articles picking up on her larger lower half.

Her new management team have sent her to "Body Doctor" David Marshall in Primrose Hill, who has been giving her intensive diet and training sessions to help her tone her legs.

Now and then: Lily Allen showed off her leaner look at Fashion Rocks earlier this month

The fitness guru, who is famous for bringing model Sophie Dahl from a size 18 to a 12, has put Lily on his six-week one-on-one course.

And the results are not just showing on her lower half - the 22-year-old is also noticibly thinner in the arms and face.

The singer has cut out sugar and wheat, and is on a diet of fish, lean meats and steamed vegetables.