Can something really have zero calories? The truth about zero-calorie foods

October 17, 2025 •

4 min read

According to the Food and Drug Administration (FDA), a product can be labeled "zero calories" if it contains fewer than 5 calories per serving. This regulation challenges the common belief that some foods are completely calorie-free and raises important questions about what consumers are actually ingesting. Understanding this labeling rule is the first step toward deciphering the truth behind the marketing of "zero-calorie" products and making informed dietary choices.

Quick Summary

This article explores the reality behind zero-calorie foods, examining how labels are regulated and the different ways products achieve their near-zero-calorie status. It debunks the "negative calorie" myth, explains the science behind fiber and indigestible ingredients, and contrasts these items with naturally low-calorie whole foods, providing insights for mindful and nutritious eating.

Key Points

Labeling Regulations: The FDA allows products with fewer than 5 calories per serving to be labeled as "zero-calorie," a regulation that can be misleading if portion sizes are small.
The Truth About Sweeteners: Artificial sweeteners provide zero or near-zero calories because the body cannot metabolize them for energy, or only a minuscule amount is needed for sweetness.
Debunking the "Negative Calorie" Myth: There is no scientific evidence that any food requires more energy to digest than it provides; the Thermic Effect of Food is a very small part of total energy expenditure.
High-Fiber Foods Are Naturally Low-Calorie: Foods rich in fiber, like celery and leafy greens, are low in calories because fiber is indigestible, not because they burn more calories than they contain.
Mindful Consumption is Key: Relying solely on artificially-sweetened, zero-calorie products can lead to nutritional deficiencies and may not promote satiety, potentially triggering cravings.
Focus on Nutrient Density: A balanced diet incorporating whole, low-calorie foods such as fruits and vegetables is a more sustainable and healthy approach to weight management.

Understanding the "Zero-Calorie" Label: A Regulatory Loophole

The most important detail to grasp about zero-calorie products is that the label does not always mean a food contains absolutely no calories. In the U.S., FDA regulations permit manufacturers to state that a product has zero calories per serving if it contains fewer than five calories. This seemingly small allowance can lead to a surprising caloric intake, especially if a product's designated serving size is unrealistically small. For example, items like non-stick cooking spray and certain single-packet sweeteners are often labeled as zero-calorie because a tiny serving falls under the 5-calorie threshold. However, in real-world usage, a person might use multiple servings, and those calories can quietly add up.

The Science Behind Zero-Calorie Sweeteners

Many zero-calorie beverages and sugar substitutes achieve their sweetness without the energy by using non-nutritive, or artificial, sweeteners. These compounds are designed to be much sweeter than sugar but are not metabolized by the body for energy. The body either cannot break down the chemical structure or the amount used is so minuscule that the calories are negligible.

Aspartame: Composed of amino acids, aspartame is metabolized by the body but is so intensely sweet that only a tiny, calorically insignificant amount is needed.
Sucralose (Splenda): A modified sugar molecule where chlorine atoms replace some hydroxyl groups, making it indigestible by the human body.
Stevia and Monk Fruit: These are plant-derived compounds that are also intensely sweet and pass through the body without being metabolized for energy.

The Myth of "Negative Calorie" Foods

For years, a popular dieting myth suggested that some foods, particularly high-fiber vegetables like celery, were "negative calorie" because the body supposedly burned more energy digesting them than the food contained. The scientific term for the energy required to process food is the Thermic Effect of Food (TEF). While the TEF does exist, it is a very small component of total energy expenditure and is nowhere near high enough to create a calorie deficit from eating. For example, even protein, which has the highest TEF, only requires 20-30% of its calories to be burned during digestion, not 100% or more. Therefore, the idea of eating a food to burn more calories than you consume is simply not backed by science.

Natural Low-Calorie vs. Artificial Zero-Calorie

When considering your options, it's helpful to compare truly natural low-calorie foods with engineered, artificially sweetened products. This table highlights the key differences.


Feature	Natural, Low-Calorie Whole Foods	Engineered, Artificial Zero-Calorie Products
Caloric Content	Low, but not zero (e.g., celery, cucumber)	Often 0 calories per serving (can be up to 5)
Nutrient Density	High in fiber, vitamins, and minerals	Very low; may lack beneficial nutrients
Satiety Impact	Promotes fullness due to high water and fiber content	May not provide a feeling of fullness, potentially leading to cravings
Digestion	Body expends a small amount of energy to break down fiber and process nutrients	Indigestible compounds pass through the body, with no energy extraction
Effect on Blood Sugar	Minimal effect, promotes stability due to fiber	Generally no direct effect, but can be influenced by other ingredients

The Role of Fiber in Minimizing Calorie Absorption

Dietary fiber plays a critical role in how the body processes food and calories. Fiber is a type of carbohydrate that the human body cannot digest or absorb for energy. Instead, it travels through the digestive system relatively intact, adding bulk and aiding digestion. Because of this indigestibility, fiber contributes very few calories to the body, making high-fiber foods naturally low in caloric density. This is why many leafy greens and vegetables are so low in calories, not because of a magical negative-calorie effect, but because a large portion of their mass consists of water and indigestible fiber.

Balancing Your Diet: A Path to Healthy Eating

Relying exclusively on engineered zero-calorie products is not a sustainable or healthy long-term strategy. While they can be a tool to reduce sugar and calorie intake, they are not a substitute for nutrient-dense whole foods. Overconsumption of artificial sweeteners has been linked to potential health issues and can contribute to a cycle of cravings and binging due to the discrepancy between sweet taste and lack of energy intake. A balanced approach that incorporates plenty of low-calorie, high-fiber fruits and vegetables is far more beneficial for weight management and overall health. These whole foods provide essential vitamins, minerals, and antioxidants that are often missing from their engineered counterparts.

Conclusion

So, can something really have zero calories? The answer is that aside from pure water, truly calorie-free foods are exceedingly rare, and the products marketed as such often contain a small number of calories per serving. The concept of "negative calorie" foods is a myth, and the key to a healthy diet lies not in finding magical calorie-free options but in understanding nutritional science. By focusing on a balanced diet rich in whole, nutrient-dense foods, and using engineered products mindfully, you can achieve your health goals sustainably and without falling for marketing tricks.

Here's an excellent resource on deciphering food labels from the FDA.

Frequently Asked Questions

No, according to FDA regulations, a product can be labeled "calorie-free" if it contains fewer than 5 calories per serving. This can be misleading, as those calories can add up if you consume more than one serving.

Artificial sweeteners work by binding to the sweet taste receptors on your tongue. Many of these compounds, like sucralose, have a chemical structure that your body cannot break down for energy, so they pass through undigested.

No, the concept of a "negative calorie" food is a myth. While your body does burn a small amount of energy to digest food (the Thermic Effect of Food), it is never more than the calories the food provides.

Most sugar alcohols contain some calories, but fewer than sugar. Erythritol is an exception, as it is poorly absorbed and thus provides almost no calories. Excessive consumption of some sugar alcohols can cause digestive issues.

Yes, plain water is the only substance that is truly calorie-free and is the most hydrating zero-calorie beverage available.

No, relying solely on zero-calorie foods is not healthy or sustainable for weight loss. It can lead to nutrient deficiencies and may cause cravings for higher-calorie foods, potentially leading to a binge-restrict cycle.

High-fiber whole foods are naturally low in caloric density and high in nutrients. The fiber helps you feel full for longer, which can help manage overall calorie intake and support sustainable weight loss.