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Calorie Labels: What Do They Tell You?
🕑 Added 2022-12-04 13:01:00 +0000 UTC[This is a transcript with references]
I like numbers, they instantly make you sound so much more educated. So what’s with those numbers on food packings, the ones that tell you how many calories the stuff has. What do they mean? What’s this keto diet that everyone on YouTube is going on about. And what’s with the idea of measuring how much fat you burn by analysing your breath? That’s what we’ll talk about today.
First things first, what’s a calorie? A calorie is a unit of energy. It was introduced in the 19th century by Nicolas Clément as the energy that is needed to heat one gram of water by one degree Celsius. That sounds pretty lame, I know, but at the time this was cutting edge research.
Scientist had only just figured out that heat is a type of energy, and that indeed different types of energy can be converted into each other. A nice demonstration of this, that you still sometimes see in physics classes, is to convert the gravitational energy from a falling weight into the motion of a rotor that stirs water and heats it up.
This experiment was originally done by Joule. No, not this Juul. That’s Joule with ou. James Joule *also defined a unit of energy which is called, guess what, Joule. Both units, calories and Joules, are in use today, the conversion factor between them is about 4 point one eight. So, one calorie is 4 point one eight Joule. See how numbers make you instantly sound educated? But for food things it’s more convenient to work with thousands of calories at a time, so that’s kilocalories and kilojoules.
Those units were made for macroscopic objects. They are huge compared to the units we use in particle physics. For example, the currently largest particle collider of the world, the Large Hadron Collider, smashes protons into each other with a collision energy of about 10 Tera electron volts. That sounds like a lot but it’s only about 10 to the minus 7 Joule. That’s because what’s important for the LHC collisions isn’t the total amount of energy but that it’s concentrated in just two protons.
Okay, that’s physics, now what do calories have to do with food, and how did we end up counting them like insomniacs count sheep? Well, for starters you can take some food and burn it and then you measure how well you can heat water with it. This gives you a calorie-value for food. This is how calorimeters work. You literally burn the food, and we’re not talking about overdone toast here.
The human body, however, doesn’t literally burn food. To begin with, it doesn’t use 100 percent of the available energy because part of it comes out with the, erm, end products of digestion. So how do you measure how much stays in the body? Well, you measure the energy of what goes in and what comes out and subtract one from the other.
This is what Wilbur Atwater did in the late 19thcentury. And, yes, that means he literally burnt shit for the sake of science. If you thought your school experiments were crap, now you know how lucky you’ve been. The result of Atwater’s efforts was a calorie value for a gram of each of the major four food groups, fat, protein, carbo’hydrates, and alcohol.
Of those four, fat has the higher energy density with about nine kilocalories per gram. That’s comparable to the energy density of gasoline, which has about ten kilocalories per gram, and about ten times as much as TNT. Yes, that’s right, sugar and fat have a higher energy density than TNT. But like with a YouTube video, it’s not just the total energy that matters, it also matters how quickly you release it.
Atwater’s original method overestimates the energy that the body can obtain from the food, because it also counts the energy contents of fibre and other indigestible components. If one adjusts his numbers to account for this, one gets the Modified Atwater system. This is what calorie labels on food packages are still based on. The manufacturer does a chemical analysis to determine the amount of fat, protein, and carbohydrates and converts them to calories. If the food contains undigestible fibres, they get to subtract something. The final number goes on the label.
There are several problems with this system. One is commercial. While food labels are mandatory in most countries since the 1990s, the guidelines give companies a lot of leeway. For example, the US FDA says that calorie values can be up to 20 percent inaccurate. Sounds reasonable enough. But food companies have a strong incentive to underestimate calorie content, so if they have legal wiggle-room you expect their numbers to be systematic underestimates.
In 2011 a group of American researchers checked and would you believe it, they found that prepackaged meals on the average have about 8 percent more calories than listed on the label. A similar study in 2013 likewise found that the average caloric content of snack foods was more than 4 percent higher than the label said.
And filmmaker Casey Neistat collected items from American food places and had them sent to a lab for analysis. His sample included only five items, which is too small to draw general conclusions from it. But he, too, found that 3 out of 5 labels underestimated the true calorie content, in one case by as much as 50 percent. The calorie labels from Starbucks and Subway, interestingly enough, turned out to be correct.
But calorie labels have a lot of other problems. For example, they don’t take into account how much energy you have to spend on digesting the food. Simply chewing food takes up energy. And just like a video about quantum mechanics, the more compact it is, the harder it’s to digest.
One type of food for which this has been extensively studied are nuts. In a series of studies from 2011 to 2015, a group of American researchers found that the calories that the body can extract from almonds are 32 percent less than what’s on the labels. For walnuts, it’s 21 percent less,
and for pis’tachios five percent less. They also found that it matters how you process the food. If you roast or chop the nuts, then the amount of energy that you can extract goes up again.
Another factor that’s relevant for how much energy you can extract from food is whether it was cooked. Raw food is generally more difficult to digest because cooking breaks down long molecules.
The results of this were measured in a laboratory experiment on mice in 2011. The researchers fed the mice with meat that was either raw, cooked, or pounded, but otherwise the same. The mice gained most weight from the cooked food. The researchers also noted “Experienced mice tended to select cooked diets.” Experienced mice also eat their food when it’s fresh. If you let it sit, it can become hard and more difficult to digest again.
Another case in point are foods that have a high fraction of starch but can be eaten raw such as corn. When uncooked, the starch is difficult to digest and a big part of it just passes through the digestive system. Cooking starchy foods can increase the amount of available energy by more than 30%.In case it just occurred to you that eating starchy vegetables raw sounds like a good idea, quite a few of them are toxic when uncooked. If there’s some food you’ve never seen eaten raw before, there’s probably a reason for it.
Yet another problem with calorie labels are ultra-processed foods that might use fats and sugars that are industrially produced and don’t exist this way in nature. They’re also often chopped into small pieces and glued back together, all of which makes it easier to digest. But did you know, chickens don’t grow in star shapes. And since ultra-processed foods are cheap and fast to produce, financial incentives play a role here, too. Many studies have documented that the consumption of ultra-processed food is correlated with overweight and obesity. We talked about this in our earlier video.
A particularly insightful study on ultra-processed was published in 2019 by a large group of researchers from the United States and Singapore. They recruited 20 volunteers with stable and normal weight, and randomly assigned them to two groups. Each group was offered the same amount of calories with the same fraction of nutrients, but one group got highly processed food, the other not. They could eat as much as they wanted. The participants who got the highly processed food gained weight, the ones in the other group lost weight. It was a small sample, but for a paper in that research area, the p-values are remarkably small.
Another thing when it comes to processed food is that in the end we don’t care about the calories per gram, we care about the total calories. You can easily bring down the amount of calories per gram just by adding water.
Yet another issue is that there are many things that can go wrong with digestion, from food intolerances, lack of enzymes, allergies, to chronic diseases and inefficient bacterial colonies. Even the length of your intestines plays a role. Any of those factors can lead to some kind of malabsorption of one or the other nutrient. The result isn’t always weight loss, because if you lack some nutrients you might end up being hungry and eat more. Even if you’re not actually ill, it is reasonable to expect that there are individual differences in how many nutrients each of us absorbs. They say quantum mechanics is difficult to understand but it’s nothing compared to digestion.
And all this doesn’t even touch on the question how much energy your body needs to function. That depends not only on how much you move around, but also on how many muscles you have. Men tend to have more muscles, which is the major reason they burn overall more energy and why women like to keep one of them around just in case the couch has to be moved.
But even leaving aside muscles, you have to keep up bodily functions, and how much energy that takes depends on your metabolic rate. That’s partly genetic, but also partly psychological, and depends on what you typically eat. For example, for many people the result of a sudden decrease of calorie intake is that the metabolic rate goes down. That makes it harder to lose weight and is why you better not talk to me when I’m on a diet. If you eat more again, the metabolic rate might not immediately go back up, so you’ll put weight on faster. But again, it might not work like this for everybody.
Now, you can come to your own conclusion from this, but in my reading, it means that the process of energy generation in the human body is highly individual. It works somewhat differently for all of us, it changes throughout your life, and Atwater’s belief that we’d be done with four numbers seems as naïve today as Aristotle’s four elements.
That said, let’s come back to the question what those labels on the food packages are good for. They’re good at telling you what the food is composed of. But they’re at best a rough estimate for how much energy you’ll get from it. The more different ingredients the food item has, the less accurate you expect the calorie-values to be. And the question what you would do with that number anyway, given that you don’t know exactly how much you burn, is another issue.
For all those reasons, many have called for simplified labels that don’t raise the impression of false accuracy. One example for such a simplified label is called NutriScore, that’s been used in France since 2017, not to replace calorie labels but in addition to them.
The NutriScore system is now also used by companies in many other countries on a voluntary basis. This score doesn’t just take into account calories but also what amount of calories is sugar, what type of fat, how much salt, and how much fibre. Cheese has its own rule.
Unfortunately, the Nutriscore value is based on a simple algorithm that can be hacked to make unhealthy food appear healthy. For example, it’s possible to cover up a high sugar content with a high percentage of fibre. Indeed, about 21 percent of foods that are currently classified as ultra-processed come out with a Nutriscore label of A or B. And in any case, this doesn’t make the calorie labels any more accurate, it’s more like throwing up hands in defeat. Okay, just give me a colour on a rainbow scale, alright.
But what else can you do? Well, for one thing you could do it like Atwater, and measure the energy of what goes in and what comes out. That requires dedication. Also, if you also want to know how much of this energy you’re actually using, you’d have to lock yourself into a room and measure how much heat you generate. It’s called room calorimetry, and while it’s done in research labs, it’s kind of inconvenient to be locked up 24/7, even if it was all the rage in 2020.
Instead of locking yourself into a room, you could measure the decay products of your energy production, which is primarily water and carbon dioxide. Yes, that’s right, if you lose weight, you lose it primarily by breathing.
According to a paper published in the British Medical Journal in 2014, if you lose 10 kilograms of fat, you exhaled 8 point 4 kilograms of that in form of carbon dioxide and the remaining 1 point 6 kilograms are water that goes into various bodily fluids. So it turns out the secret to losing weight is breathing.
But don’t try to hyperventilate yourself into the new jeans, it’s not how it works.It means, however, that you can track how much energy you burn by measuring how much oxygen you breathe in and how much carbon dioxide you breathe out. The issue with this is that it’d require you to breathe through a mask the whole day and we know how people feel about that.
One thing that’s recently become popular is to measure what you are burning. The body has two major modes of energy generation, one is burning fat, the other is burning carbohydrates. It also has two types of energy storage, the one is fat, the other is glycogen that is made from carbohydrates. We all know where the fat is stored. The glycogen is stored in the liver and muscles. The carbohydrates that you don’t immediately use and that don’t fit into the glycogen storage are converted by to fat.
Glycogen is a simpler molecule than fat and producing energy from it is faster. The body uses it for energy-intensive motion, that may be fighting a bear or lifting weights. But the glycogen supply doesn’t last particularly long, it usually runs out after a few hours. If the glycogen storage runs out, your body has to switch to fat burning. This is why marathon runners talk about “hitting the wall”, and why many of them take sugar on their runs.
But if you’re not working out, your body either uses supplies from recent food intake or, if that’s been a while ago, burns fat. That’s most of your body, except your brain, which can’t run on fat and requires glucose to work. The brain is kind of important, so if you don’t eat enough carbohydrates to power it, the body has to convert some of the fat to an alternative energy supply for the brain. These are the ketone bodies (‘key-tone). This is where the word keto-diet comes from.
The presence of ketone bodies is a sign that your body doesn’t have enough sugar to power the brain. You can trigger this by eating mostly fat and protein and very little carbohydrate. You can then measure if you have those ketone bodies by testing either blood, urine, or breath. It’s supposed to bring some health benefits, but that’s a different story. Despite what the internet tells you, most of us don’t eat that way.
But even if you’re not on a keto-diet, burning carbohydrates is a different chemical reaction than burning fat, and each produces different amounts of carbon dioxide from oxygen intake. This is why by measuring the amount of carbon dioxide in your breath, you can tell whether you’re burning fat. You can now buy devices to do that. Reviews seem to say they are quite accurate.
What you learn from this is another question. For one, just because your body is burning fat doesn’t mean it’s burning fat from your fat cells. If you eat fat, it’ll burn that. Maybe more importantly, if you know what you’re burning after you’ve eaten it, it’s too late, which returns us to the need for food labels. It seems to me those breath-analysers might be interesting for people who want to understand better what’s going on in their body or what the effects of certain types of food are. And I do understand the appeal of numbers. But personally, in this case I think I’d rather not know.
Comments
Armando Mistral
Score! This is news I can use; once again The Man is misleading us sheep with gas-lighting. We now know the *real* reason Sabine shifted her career over to being a science uber-explainer. In her prior line of work, she had no opportunity to say things like "...burning shit.... for science!". That, and all the cheese references.
Armando Mistral
Wise move.
Rad Antonov
D. All of the above. Still, we are probably lucky to have the standardized labels. I can’t imagine anything like that getting through today. That same agency was either asleep at the switch or chose to look the other way when pharma rolled out “non-addictive” opioids.
D Brown
1: Nuts may be over represented in calories, but they make up for it in the fact that they are not very filling (voice of experience). 2: I have read the glucose in your system is depleted about 12 hours after your last meal, at which point far burning kicks in. This forms the basis for intermittent fasting. 3: I have also read that the liver can produce all the glucose you need, so carbs are not an essential nutrient. In the same reading it was indicated that Ketones are a better (or cleaner) fuel for the brain in that brain function is improved. Having said that, it takes some time to get use to the change (voice of experience). P.S: The above are opinions based my memory. They can easily be proved/disproved using your favorite search engine.
I relish delivering an endless slew of random, mostly bad 'Your mum's a...' jokes upon my best friend/ex housemate. I took every opportunity I could to wrest such a jest whenever I heard or saw a suitably nonsense object or phrase. I sent him an online message in German the other day informing him that his mother is a wooden spoon because the word 'Kochlöffel' struck me as hilariously close to sounding like a vulgar insult. He is yet to respond to that message. I must say, well played, Tracey. 😆
Oh come now, Colleen, yo mama jokes are so old, cheap, and overused, just like yo mama who, it turns out, is so ugly, she threw a boomerang and it refused to come back. Since you're the Queen of the Comebacks, I will just formally concede now and cede the floor to anyone who wants to challenge you for the crown.
In 1990, the US passed The Nutrition Labeling and Education Act that was supposed to provide people with nutrition and calorie information in a standardized way so they could make informed decisions about their food intake. While I personally find this information useful, and I get a lot of annoyed people making their way around me in the aisle as I'm inspecting packages, too many people ignore the information. I do wonder if the calorie information is too technical for the average American or they are just too lazy to educate themselves or if the internet is so full of nutrition bullshit information that they can't figure anything out.
Thanks Sabine, as always! One thing isn't clear: if Adwater measures the difference between output and input, how are indigestible fibers not counted? Is it that they stay much longer in the digestive track and therefore aren't measured, and somehow the fiber content of the measured 'output' isn't exactly the same?
@Sabine: "Your mama's so fat she beat my mum in a 'your mum's a...' competition." 😀
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