If you tried to recall everything you ate and drank yesterday, chances are you’d forget a thing or two (or five), and that’s completely normal. Unless you consciously set out to think through everything you put in your mouth, it’s easy to forget about a free sample at the market, a few nibbles while cooking, or a taste from your partner’s plate. Trouble is, those unacknowledged extras can add up quick, and get in the way of weight loss and health results. What’s more, you may be engaging in unhealthy patterns you’re not even remotely aware of. The solution: start keeping a diary.

A Kaiser Permanente study involving more than 1,600 people found that those who kept a daily food journal lost twice as much weight over six months (18 pounds versus 9) compared to those who weren’t regular recorders. Another recent study, published in the Journal of the Academy of Nutrition and Dietetics, found that overweight and obese women in diet only or diet plus exercise weight loss groups all lost weight. But those who kept food journals shed six extra pounds.

Here are six key insights you may gain from tracking your intake, plus how each one can affect your ability to slim down.

Why you eat when you’re not hungry

I ask my clients to record not just what and how much they eat, but also how they feel emotionally at mealtimes, as well as their hunger and fullness ratings before and after eating. Many realize they’re triggered to eat not by physical hunger, but because they’re bored, sad, angry, or worried. Others notice that they eat to pass time when procrastinating, or out of habit, such as always having a snack while watching TV. This kind of insight is invaluable, because triggers and patterns are often unconscious, and you can’t change something you don’t even realize you’re doing. Keeping a journal changes that, because it allows you to identify the “whys” of your choices, systematically work on forming new habits, and find non-food ways to cope with emotions.

How your dining companions affect your habits

After starting a diary, one of my clients was shocked to learn just how much more she ate with her hubby compared to dining solo or with friends. Not only were the two “partners in crime” who enjoyed indulging in things like ice cream together, but they often split pizzas and ate similar portions, even though his needs were far greater than hers. It took making this connection for her to realize that gaining 15 pounds since they moved in together wasn’t just about getting older, and she felt empowered to make changes that led to weight loss. If you’re in the same boat, check out my previous post Is Your Partner Making You Fat?

How much you’re really eating

In a fascinating study, Cornell University researchers used a hidden camera to spy on patrons at an Italian restaurant. Just five minutes after the meal was over, they asked diners how much bread they had consumed. Most people ate about 30% more than they thought, and 12% of people who were seen eating bread on camera denied having any at all. The results aren’t shocking, because eating is often mindless. When you’re chewing food and distracted at the same time—whether by carrying on a conversation, checking e-mail, or watching TV—it’s easy to lose track of what or how much you downed. Recording your intake forces you to pay attention and offers a real time reality check. Even texting can help. A Duke University study of obese women who participated in a six-month weight-loss intervention found that those who tracked their intake via text lost weight, while those who didn’t gained pounds.

How fast you chow down

Journaling often triggers major light-bulb moments among my clients about just how quickly they eat. When one began tracking, he noticed that he was always the first one to finish his food when dining with others, and even alone he wolfed down sandwiches and snacks at lightning speed. As a result, he often experienced heartburn and felt unsatisfied, even when uncomfortably full. Just slowing his pace led to eating less over a longer stretch (but enjoying food more), sipping more water, ending meals without digestive upset, and, before long, tightening his belt a notch—pretty huge payoffs for one small change.

How you feel after eating certain foods

In my opinion, one of most important insights gained from food journaling is connecting what and how you eat to how your body feels. When I ask my clients to track things like energy, mood, mental clarity, and digestive happiness in their food diaries, they’re often blown away but what the find. Recently one client realized that having a veggie-packed salad topped with quinoa, lean protein, and avocado for lunch left her feeling like a million bucks all afternoon, while heating up a frozen processed meal left her feeling sluggish, grumpy, and unmotivated. As a result, she began bringing lunches to work, eating clean in order to feel better, and losing weight.

If your perceptions match reality

My clients frequently make comments like, “I eat tons of fruits and vegetables” or “I don’t drink that much,” but when they begin to track, they realize just how far off their perceptions are from reality. It’s essentially human nature—we like to recall our successes and perhaps even exaggerate them. But telling yourself nutritional white lies can hold you back from reaching your goals, or even cause you to abandon them altogether. The point of a food journal isn’t to judge or police yourself, or even to grade yourself; it’s to learn about yourself, which is the first step toward adopting healthy changes that stick!

Get started!

Find a paper form at http://pwlclincoln.com/food-logs/ or use www.myfitnesspal.com for paperless tracking.  Find the method that works best for you and get started tracking this week.