According to studies, people who keep a food diary are more likely to lose weight and to keep it off. Not only is it important to see what you have eaten, it may be just as helpful to see what you didn't eat! According to Kent Sasse, M.D., a weight-loss expert at the University of Nevada School of Medicine, knowing how many calories you almost consumed but avoided can provide much-needed motivation. So if you are struggling with weight-loss, try keeping a food diary at least for a few weeks. You will soon learn what causes you to gain and what helps you control your weight. I also recommend a food diary for anyone who has just been diagnosed with diabetes. I did that and very quickly learned what would cause a blood sugar spike and what I could eat without raising my blood sugar levels.
Your food diary can be as simple or as complicated as you like. Personally, I kept mine in a spiral notebook one page per day.