"Poker Face" Reveals Lady Gaga's Food, Weight, Psychological Issues

VIDEO: Lady Gagas former tour manager says she stays thin with extreme dieting.PlayABCNEWS.com
WATCH Ex-Manager: Gaga Has Eating Disorder

Lady Gaga's career may be in the stratosphere but a new unauthorized biography reveals that her breathless journey to the top was not a smooth trajectory.

In "Poker Face: The Rise and Rise of Lady Gaga," which comes out September 14, author Maureen Callahan discloses that Lady Gaga -- one of the world's most image-conscious pop stars -- has weathered her share of weight, food and psychological issues.

VIDEO: PETA decries Lady Gagas decision to pose in a dress made of raw meat.Play
Lady Gaga Shocks With Raw Meat Dress

"We haven't seen a character like this since Madonna and Prince, and Gaga has done [her career] so much faster and exploded in a bigger way," Callahan, a reporter at the New York Post, told ABCNews.com. The author opted to write the book independently, without her subject's involvement, so that she could freely approach whomever she wanted for information. She has never interviewed Lady Gaga.

It was Lady Gaga's uniqueness -- Callahan calls her "quick-witted, defiant and funny" and the fact that she has not made many career missteps -- that drew the author to her subject.

SLIDESHOW: Octavia Spencer's Spanx Problem

"The book shows Lady Gaga is more different than you ever thought," she said. "To me, she's one of the biggest contradictions, ever."

Callahan said Lady Gaga's poor eating habits seem to have begun when she signed with Rob Fusari, her first producer.

"It was made clear to her by her people that she needed to have a certain look," said Callahan.

One source mentioned that the artist often fumed while seeking a record deal because people weren't looking at her.

The game changer, said Callahan, was when Lady Gaga began doing photo shoots. A month before a key shoot, she dropped 20 pounds.

"All pop stars get this pressure put on them," says Callahan.

SLIDESHOW: Kardashian Claims Airline Took 'Items'

Callahan suggested that Lady Gaga, who's been touring for nearly two years, would not have been able to keep up the pace without proper nutrition. Then again, contradictions seem to be what Lady Gaga is all about.

The revelations in "Poker Face" are a cautionary tale for young artists obsessed with conceptualizing an image revered by media and fans, and aspiring to the iconic heights of fame, popularity and the paparazzi. What you see when eyeing a celebrity package isn't always what you get. And, according to "Poker Face," this seeming contradiction applies to Lady Gaga as well.

The book hits on several key areas that call into question how prepared Lady Gaga, born Stefani Joanne Germanotta, is to handle the ups and downs of fame. After all, she's only 24-years-old.

Kellie Pickler Shows Off Her Beach Bod
SLIDESHOW: Kellie Pickler Shows Off Her Beach Bod

Below, five shocking revelations from "Poker Face:"

On Gaga's diet circa May 2009: She was suffering from lack of sleep, perpetual jet lag, and a rigorous, self-imposed diet. "She'd say, 'I can't have that, I can't have that,'" David Ciemny, Lady Gaga's former tour manager says. "She always wanted salads, deli meat and cheese, and hummus and chicken -- that was her big thing, hummus and grilled chicken. If she had something fried, she'd say, 'I totally splurged.'"

Like just about every other famous young girl, Lady Gaga had to keep her weight at a ridiculously low level. "From the first time we met her and measured her and checked her for the final [ensembles], she'd lost twenty pounts," says a costumer who worked with her last year. "She self-proclaimed that she didn't eat for weeks to fit into the clothes."

VIDEO: Lady Gagas former tour manager says she stays thin with extreme dieting.Play
Ex-Manager: Gaga Has Eating Disorder

Maureen Callahan's "Poker Face."

On how Gaga regained her energy: Angela, Ciemny's wife and Gaga's former personal assistant, thinks Gaga's only escape was the hospital. "I think these were times when it was like, 'I can't be pushed. I need to check out.'" The usual course of treatment, David says, was an IV bag filled with saline and electrolytes and a B-12 shot for energy.

On Gaga's neediness, circa 2008: She couldn't be on her own, not for a minute, not even to take a shower or a nap. ... Gaga had recruited David Ciemny's wife, Angela, to work as her personal assistant, with the promise that she'd be "really nice" to work for. Angela says she was reluctant; she'd wanted David off the tour so she could conceive. Gaga convinced her: "She said, 'Angela, if you come on tour with me, I'll let you sleep with David so you can get pregnant.' And she would tell me, every night, 'OK, Ange, you and Dave can go in the back of the bus from ten o'clock to midnight.'"

VIDEO: A Bulgarian man turns to plastic surgeons to help him look like Lady Gaga.Play
Man Wants Sex Change to Look Like Gaga

In reality, says Angela, she wound up sleeping with Gaga more often than her own husband. She says there was nothing sexual about it; Gaga couldn't sleep without someone next to her in bed.

On Gaga's physical insecurities: For all her bravado on the set, [photographer Warwick Saint] says, "she had a bit of a complex about her nose. She was considering having it done, but I told her not to."

On Gaga's act at a burlesque bar in New York City's Lower East Side, circa 2007: "She would do some grinding, get down to pasties and a G-string. She was bringing in some interesting and odd elements ... "It was a strip show," Fusari [Gaga's first producer] has said. "I was like, anyone who came to that show didn't come for the music. And it really started to bother her father. I think now he knows it's part of the act, an extreme, 'Alice in Wonderland'-type thing."