Are negative-calorie foods fact or fiction?

Of all the questions we are asked as personal trainers, one which crops up more than most is this – is there such a thing as a negative-calorie food? In other words are there any food stuffs which burn calories whilst you chew? Well, the fact is there aren’t, more’s the pity. If there were it would be a dieter’s dream. The truth is it’s nothing other than an urban myth. The facts are simple when you scrutinise them:

  • There is no research to suggest any foods burn more calories than they create

 

  • Some foods have components that can help boost metabolism

 

  • Those benefits help burn some extra calories, but not a significant amount

According to Tim Garvey, chair of the department of nutrition sciences at the University of Alabama, Birmingham, negative-calorie foods could exist in theory, but the reality is in fact quite different. Speaking to the BBC’s Health Correspondent he said:

“A negative-calorie food would by definition consume more calories, for the body to handle it and process it, than is contained in the nutrient content in the food. Theoretically that’s possible- in actuality there are no negative-calorie foods.”

As a doctor whose principle focus is obesity and nutrition, Dr Garvey maintains that the only real way to lose weight is the boring, old-fashioned, unsatisfying yet ultimately successful method: eat fewer calories than you burn through exercise – not digestion.

So where does the concept of negative-calorie food come from? Well, consider foodstuffs like celery. This vegetable is often believed to be a negative-calorie food because it is low in calories, high in water content and rich in fibre content. What’s more it’s hard work to eat. Surely if ever there was a negative-calorie foodstuff, celery has to be it? Not according to the good doctor:

“While all that chewing and digesting of the fibrous food does burn calories, it doesn’t burn a lot. There may be just 10 calories in a larger stick, but the body takes only one-fifth that much to process. It’s still calorie plus.”

However he was keen to stress that celery sticks, and other high-fibre and water-heavy vegetables do have a place in any weight-loss programme. They are useful as part of a balanced and calorie-controlled diet because they can help to fill you up, and keep you from ingesting more calories later on.  

But are there other things you can eat or drink that are supposed to work in a different way, by making the body work harder? Well, there have been some suggestions. Take cold water for example. The body has to warm up cold water to a temperate of 37C (98.6F) before it can ingest it comfortably, so the body has to burn calories to bring it up to temperature. Is that not an example of a negative-calorie foodstuff?  Well, that, too, turns out to be something of an urban myth, according to David Grotto, a nutritionist and author of The Best Things You Can Eat:

“There’s no research to say that cold water drinkers burn more calories. Any amount of metabolic hit is not a significant amount – maybe five calories.”

Other foods also have different ways of increasing the rate at which we burn calories by increasing the metabolism: foods like caffeine, guanine, taurine and green tea extracts. Yet for all their benefits, there is still no such thing as a magic bullet.  Besides, Dr Garvey is sceptical about the sort of changes to the metabolism that such foods bring. He believes they cannot really lead to weigh loss. At the end of the day the only way to shed those extra pounds is to carefully control what you eat and to exercise.

 

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