Myths busted: Does eating celery create 'negative kJs'?
Catherine Saxelby takes a reality check on celery.
Ever heard of ‘negative kilojoules’? It’s a slick marketing term and the myth goes like this: Eat a stick of raw celery (theoretically containing 15 kilojoules, or 4 calories) and it’ll require a lot of chewing and digesting; being moved through the gut and chemically broken down along the way. More than 15 kilojoules are expended, and your body has to get the energy to digest it from somewhere, so it’s forced to draw the kilojoules it needs from your body fat. And bingo! You lose weight. Sounds like a dieter’s dream!
Entire websites and diet books claim that negative kilojoule foods are much harder for the body to use, and ‘burn’ more energy than the body extracts. They also imply that these foods have some amazing natural fat-burning advantage and that the more you eat, the more you’ll lose weight.
But the list of ‘negative kilojoule’ foods they’re talking about, are the same low-kilojoule ‘free foods’ that you can munch on to your heart’s content without much concern for weight gain; such as asparagus, broccoli, cabbage, carrot, cucumber and zucchini. So there goes that idea!
There is research to say that chewing and eating whole foods (ones with their physical structure intact, such as fresh celery) can be helpful for weight loss. Studies have found that the fat in whole nuts, for example, is somehow ‘trapped’ within the fibrous part and excreted. So when you eat whole nuts, you don’t absorb as many kilojoules as you would from nuts that are ground up. Using that theory, it’s thought that other fibrous foods might result in less ‘net kilojoules’ than their more processed counterparts, traditional oats versus quick oats for example; or other fibrous foods – like celery.
Basically, if you’re looking to lose weight, this is yet another good reason to eat unrefined foods that are high in fibre. But while you may indeed ‘save’ some kilojoules by eating whole foods like celery, that is still just a drop in the ocean compared to the doughnut you have just polished off. So adding celery to your lunchtime meal may help, but it won’t make a lick of difference if you’re eating it with a side of deep-fried, kilojoule-dense, nutrient-poor junk!
Trying to lose weight? There’s nothing wrong with celery – it’s filling, extremely low in kilojoules and takes time to chew. And if your mouth is full of celery, there’s no room for chips or cake. But, like any other food, it’s not a magic cure-all.