A: You're not the only one! Large portions - the "supersize" factor - play a central role in the current obesity epidemic. A recent series of studies showed how easily people fall into the habit of consuming oversized portions. In one clinical trial, researchers from Penn State University tracked the food consumption of nearly two dozen adults for 11 days. First, they gave their volunteers standard sized servings. Then they gave them portions that were 50 percent larger. The participants consistently ate more when they were provided with more to eat. The only limit the participants in this study placed on themselves was for vegetables - they didn't eat as many of them as they did of the other types of food available.
Another study from Brown University showed that the more snack foods people are given, the more they consume. The researchers wanted to know if the size of packages that snacks came in would influence how much people would eat. They gave chips, candy, cookies and crackers to 28 healthy college students. Some of the students got big boxes of snacks containing a total of 4,350 calories; other got the same amount of calories and the same amount of food divided into four small boxes. Two other groups got small or large boxes of snacks that added up to 8,750 calories. They were told to eat as much as they wanted, not to eat any other snacks and to return the leftovers three days later. The students who got the 4,350 calories all ate 60 percent of the snacks, regardless of packaging; those who got the 8,750 calories ate 81 percent more calories.
And a study at Baylor College of Medicine found that even little kids will eat more when given more to eat - but the researchers also found that children aged two to nine ate less when allowed to serve themselves.
All of this is pretty discouraging given the large portions we're faced with these days, particularly in restaurants. You can safely assume that most portions at restaurants are too big - split meals with friends or take half the meal home. The only food group you don't have to worry about over-consuming are vegetables, as long as they aren't drenched in oil or butter. At home, you can measure your portions, and in time, you should be able to eyeball servings of various types of foods. Or you can base your judgment on the suggestions below from the American Diabetes Association:
A 1/2 cup serving of canned fruit, vegetables, or potatoes looks like half a tennis ball;
Three ounces of meat, fish, or chicken is about the size of a deck of playing cards or the palm of your hand;
A one ounce serving of cheese is about the size of your thumb;
A one cup serving of milk, yogurt, or fresh greens is about the size of your fist;
One teaspoon of oil is about the size of your thumb tip.
Andrew Weil, M.D.