About a month ago we changed the brand of apples we buy at home. We switched from the large-sized “Red Delicious” apples we usually buy at the wholesale store to the medium-sized “Washington” apples from a local grocery store.
Although this was not a decision based on the size of the apple, (just that wholesale quantities of apples used to spoil faster in the summer), it had an unintended consequence: we were still getting our “apple a day”, but from a medium apple instead of the bigger one and as a snack it still kept us just as satiated until the next meal.
It didn’t take me too long to figure it out, though, because a recent study explains exactly what happened. In a paper titled “Unit bias. A new heuristic that helps explain the effect of portion size on food intake”, researcher Andrew Geier of the University of Pennsylvania explains this phenomenon:
People seem to think that a unit of some entity (with certain constraints) is the appropriate and optimal amount. We refer to this heuristic as unit bias. We illustrate unit bias by demonstrating large effects of unit segmentation, a form of portion control, on food intake. Thus, people choose, and presumably eat, much greater weights of Tootsie Rolls and pretzels when offered a large as opposed to a small unit size (and given the option of taking as many units as they choose at no monetary cost).
Additionally, they consume substantially more M&M’s when the candies are offered with a large as opposed to a small spoon (again with no limits as to the number of spoonfuls to be taken). We propose that unit bias explains why small portion sizes are effective in controlling consumption; in some cases, people served small portions would simply eat additional portions if it were not for unit bias. We argue that unit bias is a general feature in human choice and discuss possible origins of this bias, including consumption norms.
-Abstract of “Unit bias”. (Read the full paper (PDF))
Simply put, “Unit bias,” is the tendency to think that a single unit of food - a bottle, a can, a plateful, or some more subtle measure - is the right amount to eat or drink. It explains why, for example, people who used to be satisfied by a 12-ounce can of soda may now feel that a 20-ounce bottle is just right.
“Whatever size a banana is, that’s what you eat, a small banana or a big banana, whatever’s served on your plate, it just seems locked in our heads: that’s a meal,” said Geier who works with people who are already fighting obesity and eating disorders. He feels that people take cues about portions and serving sizes from their own cultures - for example in France they use smaller yogurt cups than in the U.S., but still feel ok eating just the one cup.
-Via Washington Post Health.
To prove his case, Geier and his team tried a variety of experiments with things like M&Ms, tootsie rolls and pretzels. In each case he noticed that the quantity people ate out of a bowl of these goodies depended on the size of the scoop!
Larger portion sizes in restaurants are, unfortunately, changing people’s perception of what a “meal size” is. One recommendation that many experts give is to request that the meal be split in two in the kitchen, with half on the plate and the other half packaged to take home (or just split the meal with your partner). Another idea is for dieters to use smaller plates to reduce the amount of food that “looks like a meal”.
No wonder my medium apple feels alright now (but give me a larger apple tomorrow and within a couple of days that will feel alright too!)
[tags]health, fitness, portion control, unit bias[/tags]
