Dreamstime_s_13876852If you're like most Americans, chances are you turn to a product's nutrition label for guidance on whether or not it's good for you. A 2010 American Dietetic Association study (with over 10,000 participants) found that 61.6 percent of respondents regularly examined the Nutrition Facts Panel. And with 2011 marking the 20th anniversary of required nutrition labels on products, most of us have gotten pretty good at scanning the label to find out the calories, fat, sugar, and vitamin content in our favorite foods.

But while the quantities that appear on the left of the label– 125 calories per serving, 6 grams of sugar– are pretty straightforward, the percent daily value that appears on the right is anything but. Most regular readers of nutrition labels know that the percentages of fat and nutrients a serving of a given food provides us are based on a 2,000-calorie diet, and many of us strive to stay within that level. According to nutritionist Marion Nestle, however, the choice of 2,000 calories a day was a somewhat arbitrary figure.

"From USDA food consumption surveys, the FDA knew that women typically reported consuming 1,600 to 2,200 calories a day, men 2,000 to 3,000, and children 1,800 to 2,500," Nestle writes in the Atlantic. "But stating ranges on food labels would take up too much space and did not seem particularly helpful. The FDA proposed using a single standard of daily calorie intake–2,350 calories per day, based on USDA survey data." Nutrition educators, however, argued that 2,000 calories per day was a more effective number, since it was easier to remember and closer to the calorie requirements for postmenopausal women, the group most likely to gain weight. The FDA agreed, and the 2,000-calorie mark was set.

In actuality, Nestle notes, even 2,350 calories per day are typically insufficient for adult men and adult premenopausal women, according to double-labeled water experiments. 2,000 calories a day– almost 20 percent less than that number– are usually around the amount required by kids and postmenopausal women, she adds. Calorie needs vary widely, based on your current height and weight, your age, your gender, whether or not you want to lose weight, and other health issues. Many people need more than 2,000 calories each day, while others need less.

To get a sense of the number of calories that men and women in various age groups typically need, we pulled data from more than 6,800 female and 3,700 male ShopWell users. While this group represents our user base, not necessarily the general U.S. population, we learned some interesting facts.

On average, females need fewer calories than males, and our female group of users clustered almost perfectly around the 2,000 number; 50.6 percent of female ShopWell users needed fewer than 2,000 calories, while 49.4 percent needed more than 2,000. 42.8 percent of women in our study had caloric needs falling within 100 calories above or below the 2,000 mark– but that still means that by sticking to that number, a majority of women are consuming either too many calories, or too few. This graph shows the distribution of calorie needs among female users:

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As the graph shows, the majority of women who use ShopWell need somewhere between 1,750 and 2,250 calories, making the 2,000-calorie figure a good approximate measure of caloric needs for a woman– but not a set-in-stone guideline, by any means.

The men in our study, on the other hand, almost always needed more than the FDA's recommendation: 98.9 percent of them required more than 2,000 calories, and 80.2 percent of them required more than 2,500. Only 1.42 percent of men have caloric needs falling within 100 calories of the FDA's number on either side. Here's the chart:

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On average, the men we studied required about 2,700 calories, far more than the FDA guideline. And a remarkable 17.9 percent of them needed more than 3,000 calories, 50 percent more than the number that the Nutrition Facts Panel is based on. While this isn't an invitation to go eat a few more slices of pizza (or drink an extra beer or two), guys should be aware that 2,000 calories typically won't be enough to meet their needs. To get more healthy calories, our Head Dietitian Marci Harnischfeger MS RD recommends adding an extra serving or two of vegetables, fruit, whole grains, low-fat dairy, or lean protein to your daily intake.

Want to know how many calories you really need? ShopWell's Personalized Nutrition Label, which is based on Institute of Medicine (IOM) guidelines, can recalibrate the suggested percent daily values based on your personal profile. Just enter your age, gender, height, weight, and exercise level to get a better picture of your daily calorie and nutrient needs. To find out how many calories you need to eat each day, join ShopWell today.

Got a burning question about diet, weight, or nutrition? We'll answer it for you. E-mail us at info@shopwell.com, and you may appear in a future ShopWell blog post!