Pop star Lady GaGa was hospitalized six times last year because of her yo-yo dieting, claimed the star's ex-tour manager.

The claims emerged in new book Poker Face: The Rise and Rise of Lady GaGa, by Maureen Callahan.

David Ciemny said the "sick" chart-topper went on crash diets after gorging on crisps and cupcakes.

And she once lost 20LBS between the first and final fitting of one of her outrageous outfits.

GaGa reportedly admitted she had not eaten for weeks so she could squeeze into the gear.

"When I say she was sick, I mean physically and mentally," the Sun quoted Ciemny as saying.

Ciemny also claimed GaGa sacked 150 staff members during his 18-month stint as her tour manager in 2008 and 2009.

He said she did not think they were up to scratch, adding: "Everything had to be perfect."

GaGa caused a storm last month when she admitted she occasionally used cocaine, claiming it helped her creativity. (ANI)