Through my visits to many websites over the last 4 years, I have occasionally come across lists of foods which authors have dubbed ‘calorie deficit’ or ‘negative calorie’ foods. If such claims are to be believed then it should be possible to literally ‘eat yourself thin’. My initial belief is that these foods do not exist and that the real truth has been stretched over many years. The problem lies in the fact that some readers will take that statement at face value, whom then continue to spread the notion that such foods exist. The objective of this article is to dispel or confirm if such foods actually exist, primarily for the purpose of educating myself and others who have also seen foods labelled as this.
There is a difference between the terms ‘zero calorie’ and ‘negative calorie’ in the context of food:
Zero Calorie foods: – Foods which have “little to no calories and will not have an effect on your body ”. ‘Calorie Free’ is another term which means the same thing.
Negative Calorie foods: – Foods where the body consumes “more calories, for the body to handle it and process it, than is contained in the nutrient content in the food ”.
From what I could find, ‘zero calorie’ or ‘calorie free’ foods obviously do exist in a manner of speaking (think of Coke zero, diet Dr. Pepper, etc.). However the term ‘zero calorie’ is not strictly true for all items which are termed as such. Items are typically labelled as one of these two terms if they contain less than 5 calories (Kcal) per serving . But for all intents and purposes the calorie intake is so little that the effects are negligible by comparison to an average person’s recommended daily allowance (RDA) of 2000 – 2500 Kcal.
On the other hand, ‘negative calorie’ foods only exist in theory – in practicality they do not work effectively nor do they really exist [1, 4]. This means that articles such as “15 Foods That Burn More Calories Than They Contain ”are actually bogus, or more likely are only telling half-truths because the foods listed are usually low calorie and/or healthy foods anyway.
The most infamous of these so called ‘negative calorie foods’ would be celery – a seemingly ‘wonder food’ that would require more energy to consume than would be gained from its contents. Whilst there may be only as few as 10 calories (Kcal) in a large stalk of celery, only about 20%  to 25%  would actually be burnt up through the process of chewing etc. The point being made here is that you do indeed take in a surplus of calories and thus celery cannot be a ‘negative calorie’ food by definition.
Some of you may be aware of the human body’s ability to regulate its own internal environment i.e. temperature through a process called homeostasis . This natural effect in conjunction with a glass of ice cold water could cause the body to burn extra calories to bring that cold water to a more suitable body temperature. Unfortunately it is simply not an effective weight loss strategy as a 240 milliliter glass of water at 4 degrees Celsius would maybe burn only 8 calories (Kcal), and drinking excessively large amount of water in a short period of time is actually hazardous to your health . However I suppose the term ‘calorie negative’ could fit in the described context above due to the fact that a bodily process burns more calories than are consumed – its a crying shame that it is not practical in practice.
It is therefore my opinion, based on the above, that for all practical intents and purposes, calorie negative foods are a myth. That is not to say that these foods are not healthy nor do they help facilitate weight loss via dieting – they are quite the opposite. Celery, grapefruit, watermelon, lettuce, etc. are all great foods that can help promote a healthy diet whilst being low calorie. Ditching your chocolate bar in favour of an apple or orange will very likely help you to reduce your calorie intake and provide more healthy nutrients to your body. But the fact remains, you cannot eat yourself thin – 1000 calories of celery and 1000 calories of butter is still 1000 calories!
To summarise this brief article:
- ‘Negative calorie’ foods exist theoretically, but in reality they do not exist.
- Zero calorie and calorie negative are two terms that do not mean the same thing.
- Zero calorie or calorie free foods may actually contain a few calories, typically between 0 and 5 Kcal, but are generally insignificant compared to recommended daily guidelines.
- Drinking ice water for the purpose of burning calories is not effective and could be hazardous if consumed in large volumes. Substituting sugary drinks for water however will help reduce your daily calorie intake.
- Many foods dubbed as providing ‘negative calories’ are actually healthy, low calorie foods which could help someone meet their weight-loss targets.