5 Factors That Affect Calorie Count Accuracy

People who are trying to reach or maintain a healthy weight often count calories. These 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 make better choices about the most nutritious foods for your healthy eating plan.

Unreliable Sources

The first step in determining if your calorie count number is accurate is to consider the source. Food tracking apps and some online sources provide data uploaded by consumers. In some cases, the numbers aren't checked for accuracy.

This means that serving size, macronutrient data, and calorie counts can all be wrong. Before relying on any of these sources, it is helpful to find out if the numbers are verified.

Inaccurate Nutrition Labels

The Nutrition Facts label found on packaged foods sold in the U.S. is regulated by the U.S. Food and Drug Administration (FDA) and can be considered a dependable source. However, according to FDA policies, some variation in the stated calorie count 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,” by up to 20%, says Catherine Lee, PhD, a food scientist at Procter & Gamble. So 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. One study published in the Journal of the Academy of Nutrition and Dietetics found that commercially prepared foods have some variation in stated calorie counts.

For example, a Lean Cuisine shrimp and pasta dish stated a count of 250 calories; researchers found that it actually contained 319 calories, a difference of 28%. On the other hand, a South Beach Living turkey meal 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 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 way a food was prepared. Of course, adding oils or sauces to your food will add calories, but what if you prepare your food with no added ingredients?

Some research suggests that the cooking method may change calorie absorption. In a study conducted on almonds, for instance, metabolizable energy changed based on whether the nuts were natural, roasted, or ground into butter. Almond butter had the most calories, natural almonds the least, although the differences were slight.

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

Restaurant Data Errors

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

According to research published in the Journal of the Academy of Nutrition and Dietetics, 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.

A study published in the Journal of the American Medical Association found the same, reinforcing that many restaurants understate the calorie count of their foods. It further stated that this underreporting happens more often in foods that are labeled as low-calorie or diet-friendly.

Digestion Impacts

The way that your body digests food may also change the amount of energy it absorbs. And this can change from person to person.

While most nutrient absorption takes place in the small intestine, some of it occurs in the large intestine. Studies have confirmed that there are normal variations in the length of the colon. This raises the question about variability in nutrient absorption.

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.

So, Should You Count Calories?

If calorie counts aren’t completely accurate, should you dump your food diary and give up? Not necessarily.

If calorie counting is helping you reach or maintain a healthy weight, 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 ways to reach your goal.

Either way, calorie counts shouldn't be the sole determinant when choosing foods to avoid and foods to include in your meal plan—even if your goal is weight loss. Some foods that are higher in calories also provide greater nutrition.

For example, a frozen fudge bar might provide a 100-calorie dessert. A bowl of berries topped with whipped cream is likely to provide more calories, but it also supplies your body with calcium, vitamin C, and fiber. That makes the berries a smarter choice.

A Word From Verywell

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

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.