Sometimes I can’t believe that certain nutrition myths persist as long as they do, and negative calorie foods are definitely one of the craziest, most persistent ones out there.

The idea behind negative calorie foods is that they take more calories to digest than the calories they contain. There are also plenty of claims that these foods increase your metabolism and cause you to lose weight by ‘melting your fat’.

Dr. Neal Barnard is the author of the book ‘Foods That Cause You To Lose Weight: The Negative Calorie Effect’, which claims that negative calorie foods MELT FAT and boost your metabolic rate, among other benefits. 

You’d think that a licensed physician would have to have taken at least one physiology course that includes detailed information about metabolism, but maybe he was sick that day..or er…year…I don’t know.

Dr. Barnard and the ever-brilliant (I jest, of course) Rocco Dispirito, chef and ‘healthy living expert’ are only a few of the people who have written books about how negative calorie foods melt your fat away and rev your metabolism like a Harley Davidson on the freeway.

It all sounds very suspicious, so let’s take a look at the real science behind the claims to see if there’s any merit behind negative calorie diets.

Negative calorie foods contain less calories than it takes the body to digest them:

Malarkey. This claim has been around forever, and seriously, the 70s called: they want their diet back.

Let’s break this down with science. 

The thermic effect of food is a scientific way of saying ‘the calories your body burns digesting whatever food you’ve eaten’.

Every day, depending on what you eat – protein has a greater thermic effect of food, or calorie burn, than fat or carbs, for example – you’ll burn around 5-15% of the total calories in the food you eat, in the process of metabolizing it. (that’s for a normal, mixed diet containing protein, carbohydrate, and fat)

So if you eat 1500 calories a day, between 75 to 225 of those calories are used by your body to process that food.

Let’s now take a classic ‘negative-calorie’ food like cucumber.

Cucumber contains 8 calories per 1/2 cup.

To metabolize that cucumber, you’ll use around 0.4 calories.

Even at the highest thermic effect known to us – 30% for protein, which cucumber is not, but still – you’ll still retain 5.6 of those cucumber calories.

Cucumber might be low in calories, but it definitely has them and they definitely count. Sorry.

Negative calorie foods burn fat and stoke the metabolism:

I don’t even know what to say when confronted with this sort of pseudoscientific BS.

How does this claim even work, exactly? No one knows, because it’s just a claim. 

The actual science behind fat-melting catabolic foods aka negative calorie claims is…well…okay there is no actual science. It’s a physiological impossibility that watermelon and celery burn fat. What the what?

Your metabolism rises a bit after you eat any food, because that’s what happens when your body digests stuff. But melting fat? First of all, ‘fat melting’ is an idiotic term.

Fat doesn’t just melt away like the wax from a burning candle, and no food burns fat. The small rise in metabolism – see point #5 for more on this – does not cancel out the calories in low calorie foods.

They still count, so yes: even a truckload of celery will have a net calorie gain for you…if you can stomach it.

Negative calorie foods like cucumber detox you and flush toxins from your body:

Again with the detox and toxin flushing claims. I have a headache already from debunking this one over and over! AHHHHHHHHH!

No food flushes toxins from your body. Cucumber is a high-water food, so it will contribute to hydration of your body – like many vegetables do, and fruits as well – but it flushes nothing. It’s funny how so many people make these ‘toxin’ claims, but when confronted with the question of which toxins they’re actually talking about, they can’t come up with anything.

Detox diets and toxin flushing exist for one reason: to scare you into buying what the person is selling. Don’t buy it.

Food with a lot of fiber takes more time to digest, ‘revving’ metabolism up for longer:

Um, what?

Sorry, I just need a moment to shake my head in dismay.

High fiber foods don’t ‘rev’ metabolism up at all. Yes, fiber takes more time to digest, but this has never been shown to increase the thermic effect of high fiber food.

Eating high fiber food can help you feel fuller for longer, which in turn can help you lose weight. But increasing metabolism in any significant way? No.

Drinking ice cold water or eating hot chili pepper burns calories:

Okay. I see this one a LOT. I’m including it in here, because consistent with the ‘negative calorie’ claims, this is one that’s made to convince you that there are foods that can make you lose weight by doing nothing at all except for eating. This is also a classic example of how the media distorts actual facts.

Let’s take a look, and you’ll see what I mean:

It’s true that ice cold water is a true negative calorie food. Water has no calories, and when it’s ice cold, your body expends energy to warm it up to body temperature.

But, how many calories does your body actually use to do this? Around 5 calories a glass. So how much cold water are you going to drink per day? 20 glasses? Better grab your sweater, because you’re going to be freezing…while you pee all day long!

Chili pepper as a ‘fat burner’ is something I see repeatedly in the media. You’d think that everyone would be dropping pounds left and right with all of these claims about spicy foods. People in countries where spicy food is the norm would be super slim! Except, no.

The truth is that spicy foods do increase metabolic rate by 2 calories an hour for around 5 hours after eating them, for a grand total of around 10 calories. Not worth dumping chili peppers all over your food.

When you see nutrition claims like this in the media, always remember:

How much of this food are you actually going to eat? Do you want to be putting hot peppers on everything you eat? Are you going to drink 20 cups of freezing cold water a day?

If this food does raise metabolic rate, how long does it do this for?

How many calories will you actually burn from consuming this food? Burning your tongue is NOT worth 10 calories. Nope, nope, nope.

Following a negative calorie diet will help you lose weight fast:

It depends on what you mean by ‘negative calorie diet’.

Our friend Rocco wrote a diet/cookbook with ‘negative calorie’ recipes, and he claims that by following his plan, you’ll lose up to 10 pounds in 10 days. That sounds exceptional, until you realize that his book begins with a 10 day cleanse. 

Consuming very limited calories for 10 days will cause you to lose weight most definitely, but after those 10 days? You’re SOL, people.

His diet also cuts out foods like egg yolks and grains, both of which are not harmful (news flash, Rocco: egg yolks are not harmful, that has been roundly debunked, but looking at your diet plan, I take it you’re not big on that SCIENCE stuff).

There is ZERO, and I mean ZERO research behind cutting healthy, whole foods out of your diet unless you’re legit intolerant or allergic to them. And no, we are not ALL intolerant to grains, Mr. Wheat Belly..but that’s a whole other post.

With nutrition and diets, it pays to be skeptical. If something sounds too good to be true, it probably is. It’s so hard to know who to believe when trusted medical professionals are spouting crazy ideas as though they’re fact. And for this, I’m sorry, because you all deserve better than that from them.

Don’t believe the nonsensical, science-twisting claims about negative calorie foods. Total myth.