The 31-year-old actress is not happy with her body after having two kids and had a stand in used for the more provocative scenes, reported Life and Style magazine.
"She was crushed when filming began and she didn't have her original body back so she told producers she wanted a body double. Her body is incredible, but for her it's not good enough. She's cut out carbs, but she still isn't happy," a source said.
Alba has also reportedly been chain smoking to keep her mind off food.
"She's been chain smoking lately to keep her appetite at bay. Jessica struggled with an eating disorder in her teens and when she's under pressure to look good for a part, she can slip back into extreme behaviour," a source added.