How a Diet Has 0 Calories: The Truth About "Zero-Calorie" Foods

October 29, 2025 •

4 min read

According to the FDA, food can be labeled as 'zero calorie' if it contains fewer than 5 calories per serving. This surprising fact reveals that the idea of a diet having 0 calories is largely a myth, and it's essential to understand the truth behind these labeling regulations and marketing terms.

Quick Summary

This article explores the myth of having a zero-calorie diet by defining what is truly meant by "zero-calorie" and low-calorie foods. We explain how some foods are nutritionally dense while having negligible caloric impact, debunking the "negative calorie" food concept and providing guidance on how to safely incorporate these items into a healthy, balanced diet for weight management.

Key Points

No True Zero-Calorie Food: Water is the only item with zero calories; all other foods contain some energy.
Labeling Lies: Food manufacturers can legally label products with less than 5 calories per serving as "zero-calorie".
Negative-Calorie Myth Debunked: The idea that some foods burn more calories to digest than they contain is a myth; the thermic effect of food is negligible.
Safe Low-Calorie Approach: Focus on nutrient-dense, high-fiber, and high-water content foods like leafy greens, vegetables, and certain fruits for satiety.
Dangers of Extreme Diets: Attempting a true 0-calorie diet is dangerous, can cause metabolic slowdown, and lead to nutrient deficiencies and health risks.
Balance is Key: Effective weight management requires a balanced diet of varied foods, not an obsession with impossible zero-calorie options.

The Calorie Conundrum: Is a True 0-Calorie Diet Possible?

In short, a truly 0-calorie diet is impossible and unsafe. The human body requires energy, measured in calories, to perform all its vital functions, from breathing to thinking. The notion of a "zero-calorie" diet is built on a misunderstanding of both nutritional science and food labeling regulations. Water is the only true zero-calorie item we consume, providing hydration without any energy. All other foods, even those with very low caloric content, do contain some energy value.

The Misconception of "Negative-Calorie" Foods

The myth of "negative-calorie" foods, such as celery or cucumbers, suggests that the energy required to digest them is greater than the calories they provide. While the body does use energy for digestion, a process known as the thermic effect of food (TEF), this amount is negligible. It is not enough to create a net calorie deficit from consuming the food itself. The idea is a misinterpretation of how metabolism works, and relying on this principle for weight loss is misguided and ineffective. High-fiber, high-water content foods are great for weight management because they are low in energy density and can make you feel full, but they are not calorie burners.

Understanding Food Labels and Low-Calorie Alternatives

Food manufacturers are allowed to label products as "zero-calorie" if they contain less than 5 calories per serving. This is particularly common with drinks and condiments that use artificial sweeteners, which provide sweetness with minimal or no calories. However, consumers should be aware that consuming multiple servings can add up. Some low-calorie options are excellent additions to a healthy diet, while others can be misleading.

Comparing Low-Calorie Choices


Food/Drink Item	Actual Calorie Content	Why It's Low/Zero	Considerations
Water	0 calories	No macronutrients	The only truly zero-calorie item. Essential for hydration.
Diet Soda	< 5 calories per serving	Uses non-caloric artificial sweeteners like aspartame.	Some studies suggest artificial sweeteners may increase cravings or have other effects.
Celery	~14 calories per cup	High water and fiber content	While low-calorie, it is not a negative-calorie food.
Shirataki Noodles	< 5 calories per serving	Made from konjac yam, mostly water and fiber.	High satiety, but little nutritional value.
Black Coffee/Tea	1-2 calories per cup	Primarily water with minimal nutrients	Calories are from trace amounts of compounds, negligible overall.
Fat-Free Dressings	Varies, can be low	Reduced fat content	Often contain added sugar to compensate for flavor.

How to Build a Healthy Low-Calorie Diet

Instead of chasing an impossible 0-calorie diet, focus on incorporating nutrient-dense, low-calorie foods into a balanced eating plan. This approach helps manage weight by providing satiety without a high caloric cost.

Here is a list of effective strategies:

Prioritize fruits and vegetables: Load your plate with non-starchy vegetables like leafy greens, broccoli, and bell peppers. Water-rich fruits like watermelon, strawberries, and grapefruit are also great options.
Stay hydrated with water: Drinking plenty of water is crucial for overall health and can help with feelings of fullness. Infuse it with fruits like lemon or cucumber for flavor without added calories.
Fill up on fiber: Foods high in fiber, like many of the low-calorie vegetables, help you feel full and support healthy digestion.
Use low-calorie condiments and flavorings: Spices, herbs, mustard, and vinegar can add significant flavor to a meal without adding many calories.
Choose lean protein sources: While not zero-calorie, lean proteins like grilled chicken breast, fish, and legumes are essential for a balanced diet and help with satiety.
Include healthy fats in moderation: Healthy fats are vital for health but are calorically dense. A diet with zero fats is unhealthy.

The Risks and Dangers of an Extreme 0-Calorie Approach

Attempting a diet with an extremely low or near-zero caloric intake is dangerous and medically unadvisable. Your body needs a certain number of calories to function properly, a number known as your basal metabolic rate (BMR). Failing to meet this requirement can have severe consequences.

Metabolic slowdown: Your body will enter "starvation mode," slowing down its metabolism to conserve energy, which makes future weight loss more difficult.
Nutrient deficiencies: Very low-calorie diets often lack essential vitamins, minerals, and macronutrients, leading to fatigue, illness, and other health issues.
Eating disorders: Obsessing over zero-calorie foods can lead to unhealthy eating patterns and is a potential sign of an eating disorder.
Organ damage: In extreme, medically unsupervised cases, a very low-calorie diet can lead to damage to vital organs.

Conclusion: Focus on Density, Not Zeroes

Ultimately, the idea of a 0-calorie diet is a myth rooted in marketing and misunderstanding. While there are many delicious and healthy foods with extremely low caloric density, they are not truly calorie-free and should not be the sole focus of a dietary plan. For sustainable weight management and overall health, the key is balance. Incorporating a variety of nutrient-rich, low-calorie whole foods, staying hydrated, and engaging in regular physical activity is a far more effective and safe approach than chasing an impossible zero. For guidance on a safe, low-calorie diet, consulting a healthcare professional or a registered dietitian is always the best course of action.

Frequently Asked Questions

No, the concept of negative-calorie foods is a myth. All foods contain some calories, and while the body expends energy to digest food, the amount is too small to result in a net calorie deficit.

Food manufacturers are permitted to label a product as "zero-calorie" if it contains fewer than 5 calories per serving. This is often achieved by using non-caloric artificial sweeteners in drinks or by reducing fat and sugar to trace amounts.

Water is the only substance that is truly zero-calorie, as it contains no macronutrients like carbohydrates, proteins, or fats.

Most diet sodas contain a negligible amount of calories, typically fewer than 5 per serving, allowing them to be labeled as "zero-calorie". The calories are replaced by artificial sweeteners which the body does not metabolize for energy.

Commonly referred to as "zero-calorie" are low-calorie vegetables like celery, cucumber, lettuce, and spinach. While they do have minimal calories, they are packed with water and fiber, which helps promote fullness.

Consuming too few calories can cause your metabolism to slow down as your body enters "starvation mode". It can also lead to nutrient deficiencies, fatigue, hormonal imbalances, and other serious health problems.

Low-calorie foods can be part of a healthy, balanced diet for weight management, but they should not be the sole focus. Pairing them with lean protein, healthy fats, and regular exercise is the safest and most effective approach for long-term health.