A popular commercial years ago made the phrase, "I cant believe I ate the whole thing" famous. Several new studies show that this phrase may accurately describe U.S. eating habits. It may also help explain the increase in obesity and weight-related health problems we face today.

A study in the American Journal of Public Health showed portions sold as single servings in take-out and fast-food restaurants are two to five times larger than a standard serving size. Portions twice that of a standard serving may be appropriate for some foods, depending on the overall balance in ones diet, the number of foods in a meal and individual nutrition needs.

But the large portions shown in this study are not likely to be healthy. Researchers found that the portions of French fries, burgers and soft drinks were two to five times the portions these restaurants originally served. The number of large portions offered has reportedly increased ten-fold in the last 30 years.

A new study in the Journal of the American Dietetic Association adds more to the picture of changes in portion size. It looks at how the amount of various foods consumed per eating occasion has changed in the period between two government studies that covered the years between 1989-1991 and 1994-1996. Although smaller serving sizes were reported for a few foods, more than twice as many food categories showed significantly larger portions in the intervening years. Beverage consumption showed some of the biggest jumps in portion size. The size of servings of beer and wine increased 22 to 35 percent in this period, and soft drink portions climbed more than 16 percent. This may be an important finding, since other studies have shown that we do not adjust our eating to compensate for calories consumed from liquids as well as we do for calories from solid food.

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A close look at the data from the government studies shows that most increases in portion size were relatively small generally, 10 to 15 percent, which might be as little as an extra serving spoon. Yet these inflated portions, if continued daily, could add up to an extra 50 to 200 calories a day. Although studies suggest that our bodies adapt to fluctuations in calorie consumption by burning more or less to maintain a healthy weight, a daily increase in calories might overwhelm our ability to compensate. In theory, these increases could account for a weight gain of five to twenty pounds a year.

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We arent all increasing our portions equally. The data show not only average portion sizes, but also a range of portions listed by the thousands of people questioned. Portions reported by "light eaters" did not change much between the two studies. But a big eater in 1994-1996 ate considerably larger portions than one just five years earlier, boosting some portion sizes 20 to 30 percent.

This increase in portion size from consumer and restaurant perspectives is not simply a curiosity. A new study in the American Journal of Clinical Nutrition shows that larger portions mean people eat more. Regardless of their weight, and regardless of whether they received a pre-served portion or took their own from a serving dish, people ate more if more food was available. Although people ate a larger proportion of the smallest size entre, they ate 30 percent more total food from the largest offering than from the smallest.

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Many people focus on specific food choices as the key to good health and weight control. Although a variety of healthful foods is very important, the American Institute for Cancer Research emphasizes that how much we eat is as important as what we eat.