The actress - famous for its curvy figure - does not have the motivation to work overtime and uses exercise as an excuse to eat more.
Scarlett Johansson told Britain's OK! Magazine, "I get so bored in the gym. If I spend an hour in the morning then I feel good about myself for the next three days.
"I want, I can eat what I want - I went to the gym for an hour, three days ago."
The "Lost in Translation" beauty claims that it is not naturally sexy and relies heavily on makeup to improve its appearance.
The 23-year-old star, widely regarded as one of the sexiest women in the world, said: "I do not consider myself a sex symbol. My hair and makeup spend hours at a time plastering things about me to make me look sexy. "