The Help star is playing James Brown's mother Susie in the upcoming biopic Get On Up, and she has already lost some weight for the role.
She tells People.com, "(I'm) losing a little weight. When I say a little, I mean a little. I'm not a weight girl much (sic)."
For the diet, Davis is able to eat what she wants, but only for eight hours a day. She must fast for the remaining 16.
She explains, "They tell you not to binge, but you choose those eight hours."
"I'm a former big girl, and I like the fat burgers, the turkey fat burgers and the skinny fries. That being said, I eat a lot of low-carb (carbohydrate) pasta."