You're Eating More Than You Think: Study Reveals How Bad We Are At Judging Portion Size

In response to our obesity epidemic, psychologists have been trying to figure out when and why people overeat. There were the secretly refilling soup bowls, from which experimental subjects ate huge amounts of soup without realizing it. Unstandardized restaurant portions are growing by the year, and evidence suggests that people basically unthinkingly consume whatever's on their plate, however large that is.

Here's some more bad news: even when you eat at home, you may be judging volumes of food inaccurately. Researchers at Penn State used cereal as a test food, crushing up some batches so that the flakes were smaller than usual, and asking experimental participants to serve themselves:

As the size of the flakes got smaller, the participants poured smaller volumes of cereal into the bowl. But despite the smaller volume size, the participants were actually consuming more weight and energy content. The subjects, however, believed that they consumed about the same number of calories each time.
"When faced with decreasing volumes of cereal, the people took less cereal," Prof. Rolls says. "Yet, even though they thought they were taking the same number of calories, they ended up significantly overeating."

In other words, even though the experiment participants realized that the smaller flake cereal would be denser, and even though they compensated by serving themselves a smaller volume of cereal, they still overshot their portions in terms of calories. Unfortunately, even eating even a small number of extra calories per day can really add up to lifetime weight creep. Oops.

The moral of the story: eyeballing it just doesn't work. Get out those measuring cups and make absolutely sure that you're eating what you think you're eating, every time. Springing for more expensive individually-portioned portioned foods may be worth it, if it keeps you from having to lose weight later... as long as you don't eat multiples to compensate. And never, ever eat your cereal while reading from the box, because we all know that that's the best way to turn one quick and "healthy" bowl into four.