Unpacking the Myth: Do zero-calorie things actually have zero calories?

October 15, 2025 •

4 min read

According to the U.S. Food and Drug Administration (FDA), products with fewer than 5 calories per serving can be legally labeled as having "zero calories". This brings a critical question to light: do zero-calorie things actually have zero calories, or is there a catch for those meticulously tracking their intake?.

Quick Summary

The concept of zero-calorie foods is largely a myth due to FDA labeling rules allowing manufacturers to round down small amounts. This affects everything from natural produce to artificially sweetened products.

Key Points

FDA Labeling Rules: The FDA allows products with fewer than 5 calories per serving to be legally labeled as "zero calories," meaning many items are not truly calorie-free.
Serving Size Matters: Consuming multiple servings of a "zero-calorie" product can cause trace calories to accumulate, impacting overall intake.
Artificial Sweeteners: Sweeteners like sucralose and aspartame are non-caloric themselves but often mixed with fillers that contain trace amounts of calories.
Negative-Calorie Myth: The concept that foods like celery burn more calories to digest than they contain is a myth; the body's thermic effect is minimal.
Focus on Nutrient Density: The primary benefit of natural low-calorie foods is their high water and fiber content, which promotes fullness, not their near-zero calorie count.
Balanced Approach: Relying solely on artificially sweetened or low-calorie products may not provide sufficient nutrients and could potentially influence cravings.

The quest for lower calorie intake is a common goal for many individuals focused on weight management and overall health. As a result, products advertised as “zero-calorie” or “diet” have become wildly popular. From diet sodas to artificial sweeteners and low-energy vegetables, these items promise the satisfaction of taste without the caloric burden. However, a deeper look at the science and food regulations reveals that the story is more complex than a simple “zero” on a nutrition label.

The Truth About Food Labeling and Calorie Count

One of the most significant sources of confusion around "zero-calorie" foods comes from the rules governing how calories are reported on nutrition labels. The FDA has a specific set of regulations that allows manufacturers to list a product as having zero calories if it contains fewer than five calories per serving. This small-but-not-zero amount is considered negligible for the average consumer, but it can accumulate over multiple servings. For instance, if a diet beverage contains 4.5 calories per serving and you drink three servings, you've consumed 13.5 calories, which is far from zero. This practice applies to a wide range of products, including certain cooking sprays, sauces, and sugar-free sweeteners sold in single-use packets.

The Impact of Multiple Servings

The most overlooked aspect of this labeling practice is the serving size. Consumers often assume that a package contains a single serving, but this is not always the case. A container of a zero-calorie drink or a bottle of flavor enhancer might contain several servings. By consuming the entire package, you could be ingesting multiple times the trace calories, which can add up over the course of a day or week and potentially affect weight loss goals. Being mindful of serving sizes is crucial for anyone relying on these products to manage their calorie intake.

Artificial Sweeteners: The Calorie-Free Culprits?

Artificial sweeteners are a prime example of products that are effectively calorie-free but not in the way most people assume. These chemicals are designed to bind to the tongue's sweet-taste receptors without being broken down by the body for energy.

Aspartame (Equal®): Provides almost no calories when used in small quantities.
Sucralose (Splenda®): Contains trace calories due to the bulking agents used in the powdered packets, but the sweetener itself is not metabolized.
Saccharin (Sweet n' Low®): Another high-intensity sweetener with virtually no calories.
Stevia & Monk Fruit: Natural-source sweeteners that are also calorie-free.

While these sweeteners don't contribute significant calories, some studies have raised concerns about their potential long-term effects on metabolism, gut health, and appetite. For example, some research suggests that regularly consuming artificial sweeteners may influence the gut microbiome, though the evidence is still inconclusive.

The Myth of “Negative-Calorie” Foods

A popular myth, known as the "negative-calorie" food theory, suggests that some foods, like celery and cucumber, require more energy to digest than they provide, resulting in a net calorie loss. This is scientifically unsound. The thermic effect of food (TEF), the energy used for digestion, only accounts for a small percentage of a food's total calories—and never enough to create a negative balance. For example, a 100-gram serving of celery, which has about 16 calories, would still provide a net positive calorie gain after digestion, even if minimal. While these foods are excellent, low-calorie choices, they are not a metabolic shortcut.

Comparison: Truly Zero vs. Legally Zero-Calorie Items

To help clarify the distinction, here's a comparison of items that are truly calorie-free versus those labeled as such due to FDA regulations.


Item Category	Calorie Status	Why?	Considerations
Water	Truly Zero	Pure water contains no macronutrients and therefore no calories.	Essential for hydration and overall health.
Diet Soda	Legally Zero	Uses artificial sweeteners that the body doesn't metabolize for energy.	May contain trace calories (less than 5 per serving). Serving size matters.
Black Coffee	Truly Zero	Unsweetened, black coffee contains negligible calories from trace compounds.	Calories increase with added milk, sugar, or flavorings.
Natural Foods (e.g., Celery, Cucumber)	Legally Zero (Nearly)	High water and fiber content means a very low energy density.	Still contain a small number of calories, debunking the "negative-calorie" myth.
Artificial Sweetener Packets	Legally Zero	The intense sweetener itself is non-caloric, but the packets contain fillers like maltodextrin.	Multiple packets or larger servings can add up to a few calories.

A Balanced Perspective: Beyond the Calorie Number

Focusing exclusively on the calorie count can lead to an incomplete understanding of nutrition. High-volume, low-calorie foods, often mislabeled as "zero-calorie," are highly beneficial because they are typically rich in water, fiber, and essential nutrients. These foods can help with weight management by promoting satiety and making you feel full for longer, which reduces the urge to snack on higher-calorie alternatives. Relying solely on calorie-free artificial products, however, can potentially perpetuate a craving for sweetness and do little to provide the body with essential vitamins and minerals.

Ultimately, a healthy and sustainable diet is about balancing nutrient-rich foods, not just chasing a calorie-free label. For more guidance on healthy eating, resources like the Mayo Clinic's guide to feeling full on fewer calories provide a practical approach to diet management.

Conclusion

The phrase "zero-calorie" is a useful marketing term, but it is not entirely accurate for most products. The FDA's rounding rules and the use of trace-calorie fillers mean that many commercially available items, though very low in calories, are not truly calorie-free. The exceptions are pure water and, to a negligible extent, black coffee. While natural low-calorie options like celery and cucumber are healthy choices, the concept of a "negative-calorie" food is a myth. For those aiming for weight management, understanding the difference between truly zero and legally zero calories is essential. The key is to prioritize a balanced diet rich in nutrient-dense whole foods and to be mindful of serving sizes, even when the label says zero.

Frequently Asked Questions

The U.S. Food and Drug Administration (FDA) regulations permit manufacturers to label a food or drink as having 'zero calories' if a single serving contains fewer than five calories. This is because the amount is considered nutritionally insignificant for most people.

Yes, they can. While the calorie count per serving is negligible, consuming multiple servings of a product labeled as "zero calories" can cause those trace calories to add up over time and affect your overall daily intake.

Artificial sweeteners themselves are typically not broken down by the body for energy, making them non-caloric. However, powdered packets of sweeteners often include bulking agents like maltodextrin, which can contribute a few trace calories.

No, the concept of 'negative-calorie' foods is a myth. While it takes energy to digest any food (the thermic effect), this is a small percentage and is never enough to outweigh the calories the food provides. Foods like celery are just very low in calories.

Natural low-calorie foods are beneficial primarily because they are high in water and fiber. This high volume helps you feel full and satisfied, which can aid in weight management by reducing overall food consumption.

Some studies suggest that consuming diet beverages could potentially increase cravings for sweet, high-calorie foods, which may counteract their intended weight loss benefit. The long-term effects on metabolism and appetite are still being researched.

The healthiest approach is to focus on a balanced diet of nutrient-dense whole foods, including natural low-calorie options, rather than relying on processed "zero-calorie" products. Pay attention to serving sizes and remember that these foods are not a magic solution.