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### How accurate are Americans at estimating calories?

The holiday season is officially in full swing. For some that means decorating a tree; for others, buying presents. But for everyone, it means food – lots and lots of food. Perhaps the American tradition of late December binge eating is why losing weight is perpetually a top New Year’s Resolution, and why NBC is already heavily promoting its next season of The Biggest Loser that starts in January.

Conventional wisdom holds that one main reason Americans have trouble keeping off the pounds is that they overwhelmingly underestimate the calories in food. This is presumably the logic behind laws that require chain restaurants to display calorie counts on menus. We decided to test this conventional wisdom using our Survata research network. So we asked over 6,000 US internet users to estimate the total calories in the following 8 meals and snacks:

1. Pancake meal: 2 pancakes with butter and syrup, 2 strips of Oscar Mayer bacon, 1 cup of hashed brown potatoes (1,060 Calories)
2. Cereal meal: 2 cups of Special K cereal with 1 cup of 2% milk, 1 Thomas’ English muffin, 8 oz of orange juice (594 Calories)
3. Chicken soup meal: 1 cup of Campbell’s chicken noodle soup, 1 banana, 16 oz of Snapple lemonade (431 Calories)
4. Roasted chicken meal: 1/2 breast of roasted skinless chicken, 1 cup of brown rice, 8 oz of skim milk (446 Calories)
5. Cookies & milk snack: 3 chocolate chip cookies, 8 oz of Nesquik fat-free chocolate milk (394 Calories)
6. Carrots & pretzels snack: 10 baby carrots, 1 oz bag of Rold Gold pretzels (150 Calories)
7. Subway meal: Subway foot-long tuna sandwich, 1 bag of Doritos, 20 oz of Coca-Cola (1,443 Calories)
8. Domino’s & McDonald’s meal: 2 slices of cheese pizza from Domino’s, medium-sized order of McDonald’s french fries, 20 oz of Coca-Cola (943 Calories)

The results may surprise you. Let’s dive into the numbers.

Take your best guess

In aggregate, the calorie estimates were quite accurate. The average was within 65 calories of the actual calorie content for 4 of the 8 meals.

Against conventional wisdom, Americans in our survey did not overwhelmingly underestimate calorie content. In a previously published study, Americans underestimated calorie content 82% of the time. We also observed a bias towards underestimation, but at a much lower rate – only 62%. And on a meal-by-meal basis, the median respondent:

• underestimated for 5 meals (Subway, cereal, pancakes, roasted chicken, chicken soup)
• estimated perfectly for 1 meal (carrots & pretzels)
• overestimated for 2 meals (cookies & milk, Domino’s & McDonald’s)

Would you like fries with that?

We were most surprised by the results for fast food restaurants. Our study included Subway, which has a "healthy" reputation (thanks to millions of dollars worth of Jared ads), and the combination of Domino’s and McDonald’s, which have a less-than-stellar reputation for diet-friendly foods. Amazingly, even though the Subway meal had 500 more calories than the Domino’s & McDonald’s meal, on average the respondents estimated the Subway meal had 639 fewer calories than the Domino’s & McDonald’s meal! Perhaps Americans are too anchored to Subway as a healthy choice, and Domino’s & McDonald’s as distinctly unhealthy choices. (On a related note, we found 7 sandwiches on the Subway menu had over 900 calories, and that’s before you even throw in the chips and drink!)

Together we were right, but each of us was wrong

While average estimates were accurate (including within an impressive 5 calories – about 1% – for the chicken soup meal), individual respondents displayed a wide range of accuracy. This is a variant of the wisdom of crowds effect, which states that a group’s average estimate of a measure is often accurate even when most individual estimates are inaccurate. In fact, in our study, only 14% of respondents estimated the chicken soup meal’s calories within 10% of the actual calorie content. And no meal had even 1 in 5 people give a “close” answer:

MealRespondents within 10% of actual calories
Domino’s & McDonald’s meal17%
Chicken soup meal14%
Pancake meal13%
Cookies & milk snack12%
Cereal meal10%
Carrots & pretzels snack10%
Roasted chicken meal7%
Subway meal6%

What we learned

It our study, Americans did not overwhelmingly underestimate calories for most meals. Estimates for fast food calories were significantly misguided – but in both directions! Apparently we have been misled by those oh-so-catchy jingles.

To both our under- and over-estimated readers, as we enter the heart of holiday food season: Happy Eating to All, and to All a Good Bite.

Footnotes for our fellow data geeks

1. We interviewed 6,587 online respondents from the US on December 6-13, 2012. Each respondent provided a calorie estimate for only 1 meal. We eliminated extreme outlier responses (the highest and lowest 2.5% for each meal), leaving 6,256 responses for further analysis.
2. You can view the raw responses and the sources for calorie “actuals” here, and analyze it with Statwing.
3. You can read about the science behind calorie measurements here.
4. Our survey unit looked like this:
5. We love feedback and ideas for future statistically-oriented blog posts! Email us at contact@survata.com.
6. Disclaimer: We’re not doctors, so we can’t speak to the overall health impact of these foods. We know healthy food is about more than just calories.
7. Acknowledgements: Thank you to Greg Laughlin, Ryan White, Jacob Wenger, Susie James, and Harendra Guturu for helpful comments.
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