Written by Gaga's former tour manager David Ciemny, 'Poker Face: The Rise and Rise of Lady Gaga', claims that the hitmaker was hospitalised six times in 2009 due to her yo-yo dieting which caused her to get dangerously ill.
The 24-year-old star, who burst on the pop scene with her album 'The Fame' in 2008, goes to dangerous lengths to fit into her bizarre costumes, the Daily Mail reported.
"When I say she was sick, I mean physically and mentally," says Ciemny.
According to the writer, Gaga, real name Stefani Joanne Angelina Germanotta, would go on junk food binges while on tour and would gorge on sweets and unhealthy food.
She then would starve herself for weeks so she could stay slim in her revealing outfits. Ciemny says she once lost 20 pounds in between fittings.
The 'Bad Romance' singer has once admitted to being insecure. Gaga was bullied about her appearance while at an all-girls private school in New York.
"I had a very big nose, very curly brown hair and I was overweight. I got made fun of," Gaga had once said.
There has been speculation about Gaga's eating habits before. A rep for the singer had dismissed reports earlier this year that Gaga was just eating baby food in order to stay slim.