SARATOGA SPRINGS, N.Y. – At 170 calories per serving, Kathryn Mora figured the spaghetti was harmless. So she slurped away, eating her fill.
A closer look at the nutrition label destroyed all those warm comfort food feelings: A serving was just an eighth of the box — not the whole thing.
"I can eat the entire box, like that," said Mora, snapping her fingers.
A common pitfall when checking nutrition labels is failing to factor in serving size, according to a small study by Vanderbilt University researchers. And even when people do, they often miscalculate how much they're eating. Americans' inability to understand portion control is one reason cited for the country's climbing obesity rates.
Vanderbilt's study was conducted between June 2004 and April 2005 when the low-carb craze was at its height, so many of the questions involving serving size focused on carbohydrate counts. Researchers found only about a third of the volunteers correctly estimated how many carbs were in a 20-ounce bottle of soda.
"Most people don't realize those have 2.5 servings," said Dr. Russell Rothman, lead author of the study.
Though less frequent, the same mistakes could happen when estimating calories, Rothman said. So someone drinking a 20-ounce bottle of soda may think they're getting just 100 calories when they're actually guzzling 250.
In the study, similar mistakes were made on other foods: bagels, a microwave dinner, peanut butter, a pint of ice cream, cookies and candy. That was despite nearly all respondents saying they regularly check nutrition information.
Those with lower education levels were more likely to misinterpret labels, but mistakes were made across the board.
Set by the federal Food and Drug Administration in 1993, serving sizes are often smaller than most Americans eat in a sitting. And bigger packaging over the years may have distorted perceptions.
A serving size for a drink, for example, is 8 ounces. But a can of soda has 12 ounces and most bottled sodas now contain 20 ounces or more.
Just Three Chips Ahoy chocolate chip cookies equal a serving — and 160 calories. For Lay's Potato Chips, a serving size of about 15 chips will give you 150 calories.
And, with apologies to Madison Avenue, betcha can't eat just 15.
With two-thirds of Americans overweight or obese, the FDA recently solicited suggestions on how to tweak nutrition labels and serving sizes to make them more useful. Consumers suggested labels that reflect the entire package for foods like muffins (two servings), that are typically eaten in a single sitting.
Americans also complained that serving sizes are too small, especially for sodas and cereal. Health officials, however, worry that boosting the serving size might be taken as a cue to eat more.
Such changes could also end up fueling confusion, said Regina Hildwine, spokeswoman for the Food Products Association, which opposes sweeping changes to nutrition labeling.
The food industry has responded to the confusion in recent years with a slew of products that help people size up a serving. Chips, crackers, cookies and pudding now come in handy 100-calorie packs, and single-serving packaging has exploded in popularity.
The Vanderbilt study, which surveyed 200 people, found that overall, people answered more than two-thirds of the questions about nutrition labels correctly.
Many were confused about the meaning of "percent daily values" based on a 2,000 calorie diet. However, by far the most common mistake involved serving size; many people failed to notice the serving size number and others just miscalculated.
A pint of ice cream, for example, has four half-cup servings — but many of those in the study interpreted that to mean one serving was half the container.
"It might be wishful thinking, but mostly it's just people reading too quickly," Rothman said.
A recent AP-Ipsos poll also found that even when most people check nutrition labels, they still buy products that scream high calories and fat.
"They're not using [the labels] because they don't understand them," Rothman said.
Cathy Nonas, a registered dietitian with the American Dietetic Association, said serving size is one of the first things she teaches her patients to look out for when reading nutrition labels.
Portion control may not be the only thing that matters when it comes to eating a healthy diet but, Nonas said, it's a "big piece" of the obesity puzzle.