You decide how much information to include in your daily confessional. The process can be as simple as writing down the type of food you eat and how much. But the abridged version—"burger for lunch"—doesn't cut it if you've actually devoured a quarter-pounder with cheese, mayo and ketchup on a bun, shared a bag of chips with your friend, and had several sips of his chocolate milk shake.
You may also find it helpful to keep a tally of calorie counts, especially if you try a diary and it doesn't seem to help with weight loss. Other data to consider recording:
This information can help you see when and why you eat, and then to break destructive patterns. Some people also log their daily weight and the exercise they get.