Have you ever sat down at a restaurant, looked at the menu, and thought, I'm going to aim for the healthiest thing on the menu? You glance it over and see fettuccine Alfredo, chicken Parmesan, hamburgers and fries—and then, there it is: the turkey burger.

Perfect, right? Turkey is lower in fat than red meat, it comes with some cheese for calcium, and you can ask for the mayo on the side or not at all. Plus, you decide to get the side Caesar salad in place of fries because salad is much healthier.

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In your head, you're thinking, "That's a healthy, low-calorie, low-fat meal". Well, what you forgot to account for was all those hidden fats in that restaurant food. It turns out the turkey burger is a whopping 1,150 calories and 51 grams of fat, and the side salad is a not-so-harmless 400 calories and 31 grams of fat. You just ate 1,550 calories and 82 grams of fat in one sitting. That's almost your entire calorie allotment for the day!

Everyone at one time or another has severely underestimated our caloric intake for a meal, and probably throughout the entire day. Multiple research studies have shown that self-proclaimed "small eaters" will underestimate their energy intake when self-reporting. In one study, a small sample size of participants was asked to write down food intake for three days. Then using a procedure called doubly labeled water (DLW)—what's considered the gold standard for measuring metabolism using isotopes—the researchers were able to accurately determine each individual's intake and match it to the self report.

The self-reported energy intake using the three-day food record showed that participants thought they were eating 1,340 calories per day. The DLW energy intake revealed participants were actually consuming an average of 2,586 calories a day! When two of these study participants were supplied with their self-reported energy intakes for 28 days, they lost 1.65 pounds per week! This demonstrates they had been significantly underestimating their caloric intake.

This phenomenon of underestimating food intake is the real hidden secret of weight gain. Accurately trying to account for the energy that goes into my mouth is something I have struggled with all my life. How can you ever be successful at losing weight knowing that you most likely underestimate your calories by anywhere from 1,000 to 1,500 calories a day? Stay tuned and I will let you in on the secret for  accurately guessing your intake, which is key to losing weight.