What did you eat yesterday? A bowl of cereal for breakfast doughnut at midday hamburger and fries for lunch and a grilled chicken salad for dinner. A little ice cream before bed? What about the milk and sugar in your coffee at breakfast and the flavored creamer in your coffee at work? There was that handful of trail mix and a bite of your friend's candy bar. A diet journal gives a clear and sometimes sobering perspective on just how much you are consuming on a daily basis. Ultimately it can be a valuable tool in managing weight and health.