Do you know how many calories you consumed yesterday? The answer might surprise you. Studies show that many of us underestimate how many calories we consume—often by twenty to thirty percent—and overestimate our level of activity. One of the best ways to eliminate the guesswork is to maintain a daily food diary for at least one week. When you write down everything you eat and drink, you become much more aware of what, when, and why you eat, not to mention how much. You’re also likely to notice patterns such as skipping breakfast or eating too much too late at night. A daily food diary is a powerful resource if you’re truly interested in achieving—or maintaining—a healthy, lean body.