Willpower is fuelled by blood glucose. Therefore, acts of self-control drain the glucose. When glucose is low, self-control failures are more likely. Restoring glucose to a sufficient level usually improves self-control. Willpower can be restored by boosting blood sugar. Foods like white bread, potatoes, white rice, and sugared snacks cause boom-and-bust cycles of willpower since these foods are quickly converted into glucose. Vegetables, nuts, raw fruits, and cheese are converted more slowly, and therefore provide ‘fuel’ more progressively.