This article has been reviewed by Jeannie Versagli, RD, LDN. Jeannie is a Registered Dietitian with the Academy of Nutrition and Dietetics, a national professional organization, and is licensed in nutrition with the State of Delaware.
by Nate Widom
Discussions about negative calorie foods are all over the internet. For those looking to shed some pounds and maintain their weight, the ability to eat certain foods and reduce your overall calorie intake sounds too good to be true. But as they say: “if it’s too good to be true, it probably is.” And the science agrees: so-called negative calorie foods are nothing more than a myth.
The theory behind negative calorie foods is that if certain foods take more energy for the body to digest, chew, and dispose of than what they are worth in calories, they will result in a net caloric loss.
Most of these supposed negative calorie foods include low-calorie and high-water content fruits and vegetables. For example, celery, carrots, lettuce, broccoli, tomatoes, cucumbers, watermelons, apples, berries, and zucchini are commonly referenced as negative calorie foods. While many of these foods are low in calories and nutrient-packed, evidence showing that they can be considered “negative calorie” is lacking.
A 2019 pre-print study from the University of Alabama School of Medicine researched whether lizards could experience a negative calorie intake when eating celery. Upon eating the celery, the lizards lost 33% of the calories in the celery during digestion and an additional 43% of the calories from feces and urine. For celery to be considered a negative calorie food, the sum of both the calories lost from digestion and calories lost in feces/urine would need to be more than the number of calories consumed in the celery. Since this was not the case (the lizards absorbed 24% of the calories), celery was not found to have a negative net calorie effect in this study.
So, what about chewing, the earliest stage of digestion? Yes, people may technically burn a small amount of additional energy by chewing their food longer. However, the number of calories burned from chewing seems to be minuscule at best and likely nowhere close to the number of calories the food being chewed is worth.
We can look to a study from the New England Journal of Medicine. According to the study, chewing gum for one hour increases the energy that your body uses by only 11 calories per hour. Now, think about the amount of time you spend chewing every bite of food. Even if you spent an extra 30 seconds gnawing on that stalk of celery before swallowing, your additional calorie burn would be next to nothing.
Though the idea of net negative calorie food is misleading, there is some truth to the concepts from which it stemmed. Weight loss occurs when the amount of energy expended (i.e., calories burned) exceeds the amount of energy put into the body (i.e., calories consumed). In most cases, this is not achievable with nutrition alone. Exercise and regular physical activity are necessary to push calorie burn into the threshold needed for weight loss, even for those with a fast metabolism. So, even though no food has a negative calorie effect on its own, a caloric deficit can be achieved through frequent physical activity alongside a low-calorie diet.
In conclusion, from what we currently know the existence of “negative calorie” foods is a myth. Do not be deceived by the tempting words of internet “nutrition gurus” – these foods will not help you lose a substantial amount of weight by simply eating them.
Even though negative calories are a myth, many of the foods thought of as negative calorie options have excellent health benefits that should not be ignored. Here’s a look at some of the nutritious benefits of fifteen “negative calorie” foods, with data from Conde Nast’s nutrition data website.
- Celery: At 17.6 calories a serving, celery offers 10% of the daily value of vitamin A, 40% of vitamin K, 6% of vitamin C, and 8% of potassium.
- Carrots: A cup of chopped raw carrots is 52.5 calories but provides 428% of the daily value of vitamin A, 21% of vitamin K, 14% of fiber, 13% of vitamin C and 12% of potassium.
- Broccoli: At about 31 calories a cup, broccoli offers 135% of the daily value of vitamin C, 116% of vitamin K, 14% of folate, 11% of vitamin A, and 9% of fiber.
- Tomatoes: A cup of ripe, cooked tomatoes is only about 43 calories but delivers 91% of the daily value of vitamin C, 23% of vitamin A, 15% of potassium, 13% of manganese, 9% of vitamin B6, and 7% of fiber.
- Cucumbers: A raw cucumber is 45 calories and offers 62% of the daily value of vitamin K, 14% of vitamin C, 13% of potassium, 12% of manganese, and 10% of magnesium.
- Watermelon: A cup of diced watermelon has about 46 calories and provides 21% of vitamin C and 17% of vitamin A
- Zucchini: A cup of chopped zucchini is about 20 calories and provides 35% of the daily value of vitamin C, 14% of vitamin B6, 11% of manganese, and 9% of folate and potassium.
- Grapefruit: A serving of grapefruit is about 65 calories and offers 10% of the daily value of fiber, 80% of vitamin C, 35% of vitamin A, and 6% of potassium.
- Iceberg Lettuce: A cup of shredded iceberg lettuce is only 10 calories and provides 22% of the daily value of vitamin K, 7% of vitamin A, and 5% of folate.
- Kale: A cup of chopped kale is about 34 calories but provides 206% of the daily value of vitamin A, 684% of vitamin K, 134% of vitamin C, 26% of manganese, and 5% of fiber.
- Spinach: At 7 calories a cup, spinach provides 181% of the daily value of vitamin K, 15% of vitamin A, 15% of folate, and 14% of vitamin C.
- Blueberries: At 84 calories a cup, blueberries provide 14% of the daily value of fiber, 24% of vitamin C, 25% of manganese, and 36% of vitamin K.
- Raspberries: One cup of raspberries has 64 calories but offers 54% of the daily value of vitamin C, 32% of fiber, 41% of manganese, and 12% of vitamin K.
- Potatoes: A half cup of diced potatoes is about 58 calories but provides 25% of the daily value of vitamin C, 11% of vitamin B6, 9% of potassium, and 7% of fiber.
A Note About Zero Calorie Foods
Did you know that food advertised as “zero calorie” might be slightly misleading? As it turns out, “zero calorie” food may have some calories after all. Just like “negative calories,” zero calorie foods are also too good to be true.
According to the FDA, foods considered “Zero Calorie” can only be labeled as such if the food has less than 5 calories per serving. But watch out! These serving sizes may be misleading as well.
YouTuber Technicality breaks down some of the misleading serving sizes that companies use in his video “The Truth About Zero Calorie Foods.” As an example, he cites I Can’t Believe It’s Not Butter® spray.
While one serving is advertised as having zero calories, a single serving size is only one spray of butter. Furthermore, the company states that up to four sprays contributes an insignificant number of calories and fat, and six sprays contains 5 calories, 0.5g fat and 15mg sodium.
While many “zero calorie” foods might still not be as problematic as other foods to eat, stay vigilant and keep an eye out for misleading information.