The truth about negative-calorie foods

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The truth about negative-calorie foods

Kitchen

The truth about negative-calorie foods

Nearly everyone knows the old story about celery being a negative-calorie food. For the record, that would be a food so totally lacking in calories that the acts of chewing, swallowing, and ultimately digesting the food take more energy than the food even possesses. Thus, a negative-calorie situation is born in which the simple act of eating is a weight loss exercise in itself. It almost sounds too good to be true.

Well, that’s because it is. Celery, though no doubt an incredibly low-calorie food that clocks in at just six calories, is still a net calorie-positive food. The human body, miracle that it is, is so insanely efficient at digestion, that it burns off only two calories when digesting that same stalk of celery. So for every stalk you enjoy – if anyone is ever really enjoying celery – you’re left with a surplus of four calories.

So while the idea of negative-calorie foods may be grounded more deeply in diet columns in women’s magazines straight out of the sixties and seventies than in any actual science, writing off the concept as pure bologna might be a bit premature.

That’s because our bodies are never occupied with performing just a single task at a time. An hour of breathing takes about 30 calories. An hour of just standing still burns off 152 calories. If digestion were a gear that our bodies shifted into at the expense of all other functions, then a stalk of celery would absolutely put us ever so lightly into the black. But if you pair the act of chomping on that celery with standing for just two minutes, you’re back into negative calorie territory.

There are other hacks to be found in this razor-thin field of caloric equilibrium manipulation – namely, temperature control. Drinking an 8oz glass of water will burn about 12 calories. But drinking an 8z glass of water full of crushed ice requires significantly more energy from your body. Like, 40% more energy. But before you go freezing that sandwich you brought to work for lunch, remember the scale of what we’re talking about here: 40% more energy than 12 calories is still just 17 calories.

In 2017, scientists from University Hospitals Coventry and Warwickshire NHS Trust and the University of Warwick settled the question of celery’s negative calorie status once and for all, definitively proving that consuming the bland vegetable costs the human body more energy than it takes in when doing so. Food Unwrapped’s Matt Tebbutt was sealed by researchers in a metabolic chamber for 12 hours, where he was given only celery and a celery smoothie to ingest. Both the raw and processed celeries contained exactly 53 calories. The team successfully measured that eating the raw celery burned precisely 72 calories. Drinking the celery smoothie, perhaps surprisingly, took 112 calories.

But focusing solely on the supposed negative calorie foods themselves can limit our perspective when it comes to food and dieting. While we’ve learned that a stalk or two of celery in your stomach isn’t going to transform your midsection with some magical fat-burning property unique to the vegetable, eating low calorie foods have a a fairly obvious indirect benefit. Namely, the space inside of your stomach being taken up by that celery isn’t instead full of cheesecake, or cookies, or a cheeseburger.

A 2011 Penn State study found that people who ate a serving of low-calorie foods – in this case a salad – 20 minutes before a meal ended up consuming 12% fewer calories at mealtime than those who dove straight into their entrees. Timing too played a critical part in the study. People who ate the salad beforehand consumed 23% more of it than those who were served salad and carbohydrate-heavy, high-calorie pasta together at the same time.

With all of that said, what are these maybe-they-are, maybe-they-aren’t negative-calorie foods, anyway? Beyond the aforementioned celery, the list is comprised mainly of other vegetables that are rich in both water content and fiber. Cruciferous vegetables like cabbage, cauliflower and broccoli walk the negative calorie tightrope too, along with low-sugar citrus fruits like grapefruit and somewhat bitter berries like blackberries and some types of raspberries. Almonds, mushrooms and cucumbers are also in the ballpark. It’s important to remember that your body can’t possibly survive solely off the nutrition in these foods alone, but when added to a thoughtful, nutrient-rich diet, they can certainly take the edge off of some of the less healthy foods you might otherwise overindulge upon.

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