We've all heard the myth, that certain foods, such as celery, take more calories to digest than they contain.

So if you munch enough stalks of this green stringy goodness, you will surely lose weight, right?

Well, it turns out that "negative calorie" theory isn't accurate. It's nothing more than a myth dieters have been hooked on.

In a test, thought to be a first of its kind, lizards chowed down on celery based meals and retained around a quarter of the foods calories after digestion.

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In theory, this busts the so-called "negative calorie" food myth and suggests that many other foods such as cucumber, lettuce and broccoli follow the same principal.

Katherine Buddemeyer from the University of Alabama, lead the study, using a group of bearded dragon lizards.

The lizards were fed meals containing diced celery equal to five per cent of their body mass.

Then there faeces and urine were collected to determine how much energy was lost.

Celery and its juice can still be great for weight loss. Photo / Getty Images
Celery and its juice can still be great for weight loss. Photo / Getty Images

The lizards used about 33 per cent of the calories in the meal for digestion and about 43 per cent were excreted. Meaning that the animals retained 24 per cent of the calories

Buddemeyer wrote in the study: "By evaluating these energy trade offs, we determined bearded dragons to experience a net gain in energy from their celery meals. However, this gain is rapidly abolished by the lizard's resting metabolism."

"The same is undoubtedly true for humans," they said in the report published on bioRxiv.

"Those foods touted as negative calorie do generate a net energy gain; however this gain is quickly abolished by the body's own basal rate of metabolism."

Researchers suggested that a 60kg woman would retain around 19 to 50 per cent of the calories from these foods - assuming that 25 per cent of energy was used for digestion and 35 per cent was excreted.

The woman, however, would need to consume 12.6kg of raw celery to fuel her for the average day.

The researchers did note, however, that celery is still an ideal food for weight loss: "The central aim of the majority of weight loss programs is to achieve a negative energy balance.

"Rather than labelling such foods as 'negative calorie' it would be more accurate to pitch these foods as 'negative budget', the consumption of which will favour a daily negative energy budget, and hence weight loss."

The study has been submitted to the Journal of Experimental Biology and is under review, according to Live Science.