According to the Berkeley Wellness Letter, the "eye-mouth gap" is a term coined to describe the common practice of underestimating the amount of food one eats.

Ask a person what they ate today or yesterday and odds are their caloric estimate will be off by a considerable amount. Studies show that up to 80% of the population underestimates their food intake. (This includes lean and athletic people, too.)

Researchers have found that when queried, many obese people remember eating only about half as much food as they actually consumed. A survey in 2000 found that most adults underestimate their daily food consumption by about 800 calories. Considering that the standard adult diet is in the neighborhood of 2000 calories, these flawed estimates can add up to quite a few extra pounds and/or inches around the waist.

Meanwhile, obesity in the United States is growing at a frightening pace, despite the higher risks of stroke and heart disease faced by overweight individuals.

What's more, while they underestimate the amount of sugar, refined foods, fats, and oils they consume, people also tend to overestimate their daily intake of fruit and dairy products.

So we're consuming more calories than we realize, we're eating more junk food than we realize, and we're eating less healthy food than we realize. (It appears that we're totally in the dark about quite a few things here.)

There are a few possible reasons why a person might fail to grasp what (or how much) they are putting into their bodies. Explains the Wellness Letter:

Misreporting is seldom a deliberate deception, researchers believe. More likely, it's unconsciously done, perhaps in response to social or familial pressure, combined with wishful thinking. In addition, people don't know how much food they put on their plates. If you're trying to lose weight or improve your diet, don't trust your eyes.
Doctors suggest health-conscious consumers weigh or measure their meals to have a more accurate picture of what (and how much) they're actually eating.


Source: "What we say we're eating," Berkeley Wellness Letter. January 2003.