5 Factors That Affect Calorie Count Accuracy

Nutrition facts label

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Calorie counting is widely practiced by people who are trying to reach or maintain a healthy weight. Savvy consumers spend careful moments listing meal items in their food diaries or inputting food choices into their smartphone apps. But how do they know if the numbers they are adding are really correct?

According to some biologists and nutrition researchers, there are at least five reasons that calorie counts might be wrong. Understanding these factors may help you to make better choices about the most nutritious foods for your healthy eating plan.

Calorie Count Accuracy

There are different ways that we get nutritional information about the foods that we consume. We might read product labels on food packages or we might search the internet and get a number online. Food tracking apps provide calorie counts and other nutritional data. But some of these numbers are verified and some are not.

Consumer Sources

The first step in determining if your calorie count number is accurate is considering the source. A Nutrition Facts label found on packaged foods sold in the U.S. is regulated by the U.S. Food and Drug Administration and can be considered a dependable source. The U.S. Department of Agriculture (USDA) also provides an online nutrient database where you can get reliable calorie counts and other nutrient information for foods.

But food tracking apps and some online sources provide data uploaded by consumers. In some cases, the numbers aren't checked for accuracy. Serving size, macronutrient data, and calorie counts can be wrong. Before relying on any of these sources, it may be helpful to find out if the numbers are verified.

But what if the numbers are verified and what if they do come from a trustworthy source such as the FDA or USDA? Can you safely assume that your calorie intake is correct if you tallied your numbers with care? Maybe not, say some researchers. There are other factors that affect calorie accuracy.

Nutrition Labels

According to the policies of the U.S. Food and Drug Administration (FDA), some variation in the stated calorie count on Nutrition Facts labels is allowed.

“The calories in a packaged food product can differ from what is stated on the Nutrition Facts label and you may be getting more calories than you bargained for,” says Catherine Lee, Ph.D., a food scientist at Proctor and Gamble.

“According to the FDA, food products can contain as much as 20 percent more calories than what is printed on the label."

—Catherine Lee, Ph.D.

For example, Dr. Lee explains that a snack bar labeled as having 200 calories could potentially be 240 calories and still be within the government labeling guidelines.

Research has confirmed this discrepancy with some caveats. A study published in the Journal of the Academy of Nutrition and Dietetics found that commercially prepared foods had some variation in stated calorie counts.

For example, Lean Cuisine Shrimp and Angel Hair Pasta stated a count of 250 calories, but the researchers found that it actually contained 319 calories, a difference of 28%. On the other hand, South Beach Living Roasted Turkey had a lower calorie value than stated, 222 calories versus 212 actual measured calories.

Overall, however, study authors noted that the variations were statistically insignificant and that there were positive and negative variations in all brands tested. That is, no brand was better than the others in providing accurate numbers.

Preparation Method

Another factor that can affect calorie accuracy is the preparation method. Of course, adding oils or sauces to your food will add calories, but what if you prepare your food with no added ingredients? There may still be some variation in the number of calories your body absorbs.

For example, some research suggests that the cooking method may change calorie absorption. In a study conducted on mice, biologists found that when food is consumed raw fewer calories are absorbed than when food is cooked or otherwise processed.

It would make sense then, that buying preprocessed foods may increase the number of calories you absorb, One study, published in Food and Nutrition Research found this to be true.

In the study, test subjects consumed cheese sandwiches with identical macronutrient content. When the cheese sandwiches contained processed ingredients (refined bread, processed cheese spread) the subjects absorbed more calories than they did when the sandwiches were made with unprocessed ingredients (multi-grain bread and cheddar cheese slices).

Restaurant Meals

Dining out offers additional challenges. Not only can the preparation method change your caloric intake, but the advertised calorie count of your favorite restaurant food might be wrong. Research studies have found that what’s listed on the menu is not always the same as what lands on your plate.

A study published in the Journal of the American Medical Association revealed that many restaurants understate the calorie count of your food.

According to research published in JAMA, 19% of foods tested in restaurants contained energy contents of at least 100 calories more than the stated energy contents—an amount that could cause five to seven kilograms of weight gain per year if consumed daily.

Unfortunately, underreporting of calories happened more often in foods that were labeled as low-calorie or diet-friendly.


The way that your body digests food may also change the amount of energy it absorbs. According to biologists, there is variation from person to person. Recent studies have confirmed that there are normal variations in the length of this vital organ.

While most nutrient absorption takes place in the small intestine, some of it occurs in the large intestine. More importantly, these studies raise the question about variability in nutrient absorption from person to person. If our bodies vary in their structure, why wouldn't they also vary slightly in function? Maybe some bodies naturally absorb more calories than others.

Should You Count Calories?

So, if calorie counts aren’t completely accurate, should you dump your food diary and give up? Not necessarily. If calorie counting is helping you to reach or maintain a healthy weight then don’t ditch your plan. Calorie counts are still a relatively good way to measure food intake. But if calorie counting has not worked, this may be one of the reasons why. You may need to consider other factors to reach your goal.

Calorie counts shouldn't be the sole determinant when choosing foods to avoid and foods to include in your food plan—even if your goal is weight loss. Some foods that are slightly higher in calories provide greater nutrition.

For example, if you're looking for a diet-friendly dessert, a frozen fudge bar might provide 100 calories. A bowl of berries topped with whipped cream is likely to provide more, but it will also provide your body with calcium, vitamin C, and fiber. For a healthy body, the berries are a smarter choice.

Calorie counts are helpful, but take them with a grain of salt. Examine macronutrient (carbohydrate, protein, and fat) and micronutrient (vitamins and minerals) information to make smart choices. Then use portion control to consume moderate portions and keep your weight in check.

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