That's according to a new study in the Journal of the Academy of Nutrition and Dietetics.
Scientists found two of the most important tools of weight loss were a pen and notebook.
Women who kept food journals lost more weight , an average of 6 pounds more, than women who did not.
Skipping meals and eating out frequently, especially at lunch, led to less weight loss.
According to researchers, it's all about accountability, knowing what you're eating and how much.