If you found out that the calorie counts you’re reading on the back of food labels aren’t 100% accurate, would you find this news shocking? Like most things in life, it’s hard to expect perfection but, when it comes to calorie counting, rest assured that you don’t need perfection to reap the benefits. We’ll take you through where calories come from, and help you better understand why calorie counting is helpful.

HOW CALORIES ARE COUNTED

The system companies use to come up with calories for the nutrition facts panel is called the Atwater Method, invented by Wilbur Atwater. Food is burned in a device called a “calorimeter.” The amount of heat (also known as energy) released is used to heat water. Foods that generate more heat, and are therefore able to raise the water to higher temperatures, were higher in calories. One calorie is the energy it takes to raise the temperature of one gram water by one degree Celsius.

Fun fact: One food Calorie (notice the capital “C”), which is what’s normally found on the back of food labels, is actually equal to 1,000 calories. The Calorie is what we mean when we refer to “calories.”

PROBLEM #1: OVERESTIMATION

The problem with using a calorimeter is that it doesn’t work well on all types of food. Calorimeters more accurately measure calories from highly refined, processed carbs (think white bread, rice, pasta), but not high-fiber or high-protein foods. Meats and nuts, for example, are harder to break down by the human body and so we don’t fully extract the calories from these foods.

A more accurate calorie-counting method would take into account not only the available calories in food, but also the energy we’d need to digest and process that food. This method has been proposed by the United Nations Food and Agriculture Organization (FAO), but has yet to be adopted.

Does this mean calories may be overestimated for some foods? Yes, but it doesn’t affect us, as consumers, to any appreciable degree. It’s understandable why experts aren’t keen on making the switchover to the more accurate system:

1. Excess weight and obesity is a major problem in many countries. It might send the wrong message to say the current system is overestimating calories because it indirectly tells consumers to eat more when they should be eating less.
2. Changing the current system requires time and resources that may be better spent on more prominent issues (think heart disease, diabetes, cancer).
3. Switching over doesn’t guarantee 100% accuracy. While the new calorie-counting method may be more accurate than what we have now, it’s impossible to count calories with complete accuracy. Why? Because there’s a bewildering number of factors that affect calorie count.

PROBLEM #2: UNDERESTIMATION

The U.S. Department of Agriculture (USDA) is responsible for overseeing guidelines and compliance for the nutrition facts panel and other nutrition info for the foods we buy. They, too, understand that it’s impossible to measure calories with 100% accuracy. In their guidance for the food industry, the USDA sets up a plus or minus buffer of 20%, meaning that it’s acceptable for calorie counts to be over- or underestimated by 20%.

A small study published in the Journal of the American Dietetic Association found that foods at 29 quick-serve and sit-down restaurant foods had, on average, about 18% more calories than was stated. Ten frozen meals purchased had, on average, 8% more calories than was stated. Both categories fit into the USDA’s constraint of a 20% calorie buffer.

OTHER FACTORS CONTRIBUTING TO INACCURACY

It’s helpful to know that some foods’ calories are overstated while others are understated. Why? Because if this is the case then human estimation errors ultimately cancel each other out. Beyond estimation errors, there’s a few more reasons why calorie counts aren’t always accurate:

• Digestion varies from person to person. We’re all genetically different in the way that we handle our food. Our bodies are well-oiled machines capable of extracting calories and converting them into energy, but some bodies are better at it than others. For example, people who have longer gastrointestinal tracts (by virtue of their height) are far better at extracting calories because food stays longer in their systems. They need more calories as well.
• Cooking changes how many calories a food has. Boiling, baking, and even burning food can change how many calories a food has. Generally speaking, cooking food makes calories more readily available to our bodies. For example, cooked rice is easier for our body to digest, thus yielding more calories than uncooked rice.
• Processing changes how many calories a food has. It’s also the reason why refined carbs (think white bread, rice, candies) are so quickly absorbed and digested. Highly processed foods will contain more readily absorbable calories than non-processed foods.
• Certain gut bacteria are more efficient than others. We all have a unique gut microbiome (a collection of bacteria naturally occurring in your intestines); the good bacteria in this microbiome helps us digest food, make vitamins, keep other bad bacteria out, and so much more. Some of us just have more bacteria that are wicked good at extracting calories.

WHAT TO EXPECT FROM CALORIE COUNTING

Even though calorie counts might never be 100% accurate, tracking calories is still useful. Calorie counting is a powerful tool, especially if you’re starting out on your health and fitness journey. Here’s what you can learn from keeping track of your food:

• The number of calories in food. It’s easy to think you can just eat fewer calories and lose weight, but it’s actually very difficult to sum up the calories accurately in food, particularly if you’re a newbie. Think about the first time you learned the amount of calories in your favorite dessert, or coffee drink—were you surprised? Over time, you probably learned which foods commonly blow your calorie budget.
• Correct estimation of portion sizes. Not going to lie—we’re all still working on this. To get accurate calories from the foods you eat, judging portion size accurately is key. This is easier said than done, since most of us suffer from “portion distortion,” where we think a portion is smaller than what it is . Portion sizes have been steadily on the rise. Just compare the size of foods 20 years ago versus today: A typical bagel 20 years ago was 3 inches in diameter and 140 calories. Today, that same bagel is 6 inches in diameter and 350 calories.
• The quality of the foods you eat. Tracking your calories educates you about the quality of your food choices. It keeps you accountable for those choices, for better or worse.
• There’s evidence that monitoring your intake can help maximize weight loss. Many studies have found a significant link between keeping track of your food and weight loss. By monitoring your food, you become more aware of what you put in your body, how it makes you feel, and how it affects your weight. Over time, you learn to develop eating habits that will put you on the road to good health. While you can always track your food, exercise, weight and so forth using a paper diary, MyFitnessPal offers you the convenience of tracking from your smartphone or computer.

Do you use calorie counting as a tool to help you maintain a healthy weight? If so, share what you’ve learned in the comment section below.