TBH that's true for most foods (not necessarily less but not exactly what the label says).
The most common way of calculating the caloric value for food is by calculating the fat, fatty acids, proteins and carbohydrates by weight and assigning them the common caloric value this in itself is not accurate to begin with.
The more accurate way is going to be by testing the overall caloric potential of the food before digestion and then checking the caloric value of the fecal mater after digestion, but that isn't something easy to do.
If you are selling a hand made sandwich that data might be available for most ingredients and you'll end up having quite an accurate caloric value. But with many processed and mass produced food products that's simply not the case as it's quite hard to estimate what exact caloric value your body would extract from each portion with so many ingredients from various sources.
The biggest problem is that not all foods are digested the same way this is both universal e.g. foods with higher percentage of non soluble fibers reduce the caloric value (10-30%) and non-universal per person specific metabolism, your personal digestive track biome and many other factors like how much activity have you done before and after eating.
Eating a more or less rounded meal on an exact schedule and a very mild exercise (like a casual walk) shortly after the meal can reduce the amount of calories your body extracts from the food quite considerably.
Now it's true that genetics and some other circumstances play quite a big role, but eating on schedule and not sitting straight after heaving your food can do wonders for some one who is trying to either lose or maintain weight.
Yes burning a couple 1000's of extra calories a week at the gym can do wonders but in many cases it's not as effective as proper diet management and diet management isn't about counting calories is about finding a good combination of what your body will digest well but not over digest and teach your body that it doesn't need to hoard everything because it knows that the next meal will come on time.
When you eat regularly and induce a system in which your body would rather metabolize what it needs straight away and use that instead of hoarding everything and converting it to fat while burning your glucose reserves (which what induces the odd hour cravings) works better than just counting calories.
You can have 2 people eating at exactly their BMR with the same caloric intake and outtake and one would lose weight and the other would gain it just because one eats regularly 4-5 times a day and the other eats irregular meals and snacks when they feel hunger.
> But with many processed and mass produced food products that's simply not the case as it's quite hard to estimate what exact caloric value your body would extract from each portion with so many ingredients from various sources.
Generally speaking, processed foods are more likely to achieve the full thermodynamically available calories, because most of what we consider "processing" makes things more digestible. For example, if you create Cheetos out of corn, you grind corn into meal, then bake it or whatever. When it goes into your stomach, it readily dissolves into an easily-digestible soup of corn specks and oil. If you just eat corn, the kernels have much less surface area available for the digestion process and some parts remain (notoriously) undigested.
That means it's pretty easy to calculate the number of calories that highly processed foods contribute, since it's near the theoretical max.
In theory yes, but in practice it's much more complicated than that.
During the protein crave of the late 90's early 2000's we added protein to everything because doctors said we aren't eating enough of it.
Wheat protein was one of the easiest and the cheapest to work with which is now why we are now having to search for Gluten free dairy products which wasn't an issue 15 years ago.
After proteins fibers became the biggest crave so the food industry found another cheap source for them - boiled saw dust from pine trees.
Processed food isn't simply just ground nutrition it has some really really fucked up stuff in it (fucked up as in weird not indicatively bad).
That only matters if results differ between each person. If everyone has the same results, 18 people is plenty to prove that the results are the same for everyone. It depends on the sample variance and the number of people. If you have high sample variance, you need a higher N to make it less likely that you have a sampling error. If you have very low sample variance, just a few people is enough.
Awhile back, I tried to find the actual studies that determined that sugar has 4 kcal/g and fat has 9. I failed. I couldn't even find a clear definition of what a kcal means. (Is it mechanical work you can do after eating it? ATP produced?)
Given recent results, I wouldn't be at all surprised to learn that fat, in general, has less than 9 kcal/g or that sugar has more than 4.
The numbers the US uses for calories in fat, protein, carbohydrates and alcohol come originally from a man named Wilbur Atwater who around the turn of the 20th century calculated them by measuring how many calories someone was consuming and measuring the calories in their feces.
They've been modified over the years for specific ingredients, but we still use the Atwater system today because it is very easy for food manufacturers to use.
Europe and elsewhere use Rubner factors which are slightly different.
One calorie is the energy required to raise the temperature of one gram of water at 1 atm pressure by one degree Celsius, it is equal to about 4.2 Joules. A kilocalorie, or a dietary Calorie, is one thousand calories, or 4200 Joules. All of this is readily available from an innumerable number of sources.
The calorie content of food is determined experimentally by burning the food in a calorimeter and measuring how much heat is produced (by, for example, measuring how much it raises the temperature of a water bath). This measures the energy content of the food, but does not measure the amount of energy your body can make use of as that is a very complex problem that would have a different answer in every individual due to variations in body size, metabolism, digestion, muscle mass, insulin activity, the ambient temperature, and about a zillion other factors.
Well, in this study the calories were measured by the difference of energy released by calorimetry between the walnuts and the subjects' waste. The definition of calory in this case is obvious (and infinitely more useful than simply measuring only the energy released from igniting the food).
In the context of their post, the parent (as I read it) meant the operational, nutritional definition of a calorie, not the thermodynamic one.
That is, when it's claimed on a label, does it mean "this is what you get from burning it in a lab" or "this is how much usable energy as ATP it becomes" or "this is the ignition delta between mouth and feces"? The thermodynamic definition doesn't tell us that.
Use chemistry to explain to me how a human body converts a walnut into energy.
Hey downvoters, if Im wrong in thinking that the chemical processes involved in digestion are too complex to be coherently applied to a high level model of a human diet, then explain how Im wrong. Or am I just dumb for feeding the troll?
I'm not sure if this is me misreading your comment, but this has been extensively worked out.
We have really excellent knowledge of how metabolism works compared to a lot of other processes in biology. You learn this as the major, significant component of any introductory biochemistry class. I don't even know where to start here.
Yeah, I kinda feel like that too. I'd like to think they saw the results of other studies and just thought "Oh wow it would be great if we see the same results on our walnuts. On the other hand, the California Nut Industrial Complex could just be pretty evil.
The most common way of calculating the caloric value for food is by calculating the fat, fatty acids, proteins and carbohydrates by weight and assigning them the common caloric value this in itself is not accurate to begin with. The more accurate way is going to be by testing the overall caloric potential of the food before digestion and then checking the caloric value of the fecal mater after digestion, but that isn't something easy to do.
If you are selling a hand made sandwich that data might be available for most ingredients and you'll end up having quite an accurate caloric value. But with many processed and mass produced food products that's simply not the case as it's quite hard to estimate what exact caloric value your body would extract from each portion with so many ingredients from various sources.
The biggest problem is that not all foods are digested the same way this is both universal e.g. foods with higher percentage of non soluble fibers reduce the caloric value (10-30%) and non-universal per person specific metabolism, your personal digestive track biome and many other factors like how much activity have you done before and after eating.
Eating a more or less rounded meal on an exact schedule and a very mild exercise (like a casual walk) shortly after the meal can reduce the amount of calories your body extracts from the food quite considerably.
Now it's true that genetics and some other circumstances play quite a big role, but eating on schedule and not sitting straight after heaving your food can do wonders for some one who is trying to either lose or maintain weight. Yes burning a couple 1000's of extra calories a week at the gym can do wonders but in many cases it's not as effective as proper diet management and diet management isn't about counting calories is about finding a good combination of what your body will digest well but not over digest and teach your body that it doesn't need to hoard everything because it knows that the next meal will come on time.
When you eat regularly and induce a system in which your body would rather metabolize what it needs straight away and use that instead of hoarding everything and converting it to fat while burning your glucose reserves (which what induces the odd hour cravings) works better than just counting calories. You can have 2 people eating at exactly their BMR with the same caloric intake and outtake and one would lose weight and the other would gain it just because one eats regularly 4-5 times a day and the other eats irregular meals and snacks when they feel hunger.