a) all calories in the food you put in your mouth are digested;
This is certainly not true. Usually calories in food are measured burning the stuff and measuring the calories emitted, but of course our digestive tract doesn’t work like that.
This means that we always absorb less calories that are in the food, indeed cooking was a great revolution in human history because it allowed more calories to be extracted from the same amount of food.
b) the digested calories are either stored as fat or spent as work; there is nothing else that could happen with them;
This, on the other hand and with the caveat of a), seems pretty uncontroversial. There are different deposits of long-term energy, such as glycogen in the liver, glycogen in the muscles and adipose tissue. But other than accumulating or being used to produce ATP, I have never seen any reason to believe that calories are used for something else.
c) the calories are the whole story about nutrition and metabolism, and all calories are fungible.
Well, this is obviously untrue, but usually “calories in, calories out” is used in the context of weight loss.
Could it be that some people are forced to eat large amounts of food just to extract the right amount of vitamins and minerals, and any attempt to eat less will lead to symptoms of malnutrition?
It can be, but the body is usually extremely efficient when extracting vitamins out of food. An inability to do that would be a serious business, most probably caused by a genetic disease, and surely cured by supplementation rather than eating large quantity of food.
maybe you cannot always get thin by eating less calories than you spend working; but if you eat more calories than you spend working, you will inevitably get fat.
I don’t see how the first sentence would work. As far as I know, there are no hidden reserve of energy besides glicogen, muscle proteins and fat.
But it is possible that some of the “calories in (the mouth)” may pass through the digestive system undigested and later excreted? Could people differ in this aspect, perhaps because of their gut flora?
This is a certainty. Think for example to all the calories contained in indigestible fibers.
Also, what if some people burn the stored fat in ways we would not intuitively recognize as work? For example, what if some people simply dress less warmly, and spend more calories heating up their bodies? Are there other such non-work ways of spending calories?
That is called non-exercise activity thermogenesis (NEAT) and is the way that most of our calories are expended: keeping body temperature constant, providing energy to all the chemical reaction in the body, etc.
While reality seems to suggest that most people, both thin and fat, keep their weight stable around some specific value.
Yes, there is a set-point which is regulated by a complex interaction between various hormones, such as ghrelin, leptin, insulin, etc.
Not sure if I am reading your response correctly, so would you agree or disagree that it is possible for two people to eat the same food, do the same work, and yet one of them will be thin and the other one will be fat, because of some combination of:
different gut flora;
different genes contributing to efficiency of digestion;
different genes contributing to efficiency of keeping body temperature constant;
(other stuff I forgot to mention).
In other words, that there is such a thing as “metabolic privilege”, which is usually denied or ignored by the “calories in, calories out” proponents.
In other words, that there is such a thing as “metabolic privilege”, which is usually denied or ignored by the “calories in, calories out” proponents.
Huh? The individual metabolism (aka the “metabolic privilege”) is what primarily determines the “calories out” part. No one denies that people have different metabolisms.
The CICO theory says that the only way to lose weight is to have a negative calorie balance. You can achieve it in any way you want—by lowering the CI part, or by increasing the CO part—but it has to be there for you to lose weight.
The claims that all calories are fungible or that the CO part is stable are just strawmen.
No one denies that people have different metabolisms.
Statements including “no one denies that …” are usually false.
Regardless, my goal here was to ask people to help me decipher what “calories in” and “calories out” precisely mean, especially where the correct version could differ from the naive interpretation.
Because it seems to me that (a) the naive interpretation is wrong, but (b) most people use the “calories in, calories out” argument as if the naive interpretation is true. (“If you disagree with the naive interpretation, you ignore the laws of physics!”) Motte and bailey, etc.
Statements including “no one denies that …” are usually false.
Taken literally, yes. However these statements are not intended to be taken literally, they are a shorthand for “it is widely accepted that X is true, most people who deny X are either blatantly unreasonable or have strong incentives to do so. I do not expect sane people to deny X with a straight face”.
Regardless, my goal here was to ask people to help me decipher what “calories in” and “calories out” precisely mean
See the grandparent post. In particular, to repeat myself
The CICO theory says that the only way to lose weight is to have a negative calorie balance.
In general CICO posits one-to-one correspondence between net energy balance and gaining/losing weight, regardless of anything else. This is on a time scale where short-term fluctuations (from bowel movements to water retention) are ignored as noise.
CICO also does NOT say anything about the fat/muscle ratio, it does NOT say that different foods with the same calorie content will have the same effect on weight (food you eat generally affects both the CI and the CO parts), it does NOT say that specific levels of CI (e.g. 1000 calories/day) will result in specific gain/loss of weight.
This is certainly not true. Usually calories in food are measured burning the stuff and measuring the calories emitted, but of course our digestive tract doesn’t work like that. This means that we always absorb less calories that are in the food, indeed cooking was a great revolution in human history because it allowed more calories to be extracted from the same amount of food.
This, on the other hand and with the caveat of a), seems pretty uncontroversial. There are different deposits of long-term energy, such as glycogen in the liver, glycogen in the muscles and adipose tissue. But other than accumulating or being used to produce ATP, I have never seen any reason to believe that calories are used for something else.
Well, this is obviously untrue, but usually “calories in, calories out” is used in the context of weight loss.
It can be, but the body is usually extremely efficient when extracting vitamins out of food. An inability to do that would be a serious business, most probably caused by a genetic disease, and surely cured by supplementation rather than eating large quantity of food.
I don’t see how the first sentence would work. As far as I know, there are no hidden reserve of energy besides glicogen, muscle proteins and fat.
This is a certainty. Think for example to all the calories contained in indigestible fibers.
That is called non-exercise activity thermogenesis (NEAT) and is the way that most of our calories are expended: keeping body temperature constant, providing energy to all the chemical reaction in the body, etc.
Yes, there is a set-point which is regulated by a complex interaction between various hormones, such as ghrelin, leptin, insulin, etc.
Not sure if I am reading your response correctly, so would you agree or disagree that it is possible for two people to eat the same food, do the same work, and yet one of them will be thin and the other one will be fat, because of some combination of:
different gut flora;
different genes contributing to efficiency of digestion;
different genes contributing to efficiency of keeping body temperature constant;
(other stuff I forgot to mention).
In other words, that there is such a thing as “metabolic privilege”, which is usually denied or ignored by the “calories in, calories out” proponents.
Huh? The individual metabolism (aka the “metabolic privilege”) is what primarily determines the “calories out” part. No one denies that people have different metabolisms.
The CICO theory says that the only way to lose weight is to have a negative calorie balance. You can achieve it in any way you want—by lowering the CI part, or by increasing the CO part—but it has to be there for you to lose weight.
The claims that all calories are fungible or that the CO part is stable are just strawmen.
Statements including “no one denies that …” are usually false.
Regardless, my goal here was to ask people to help me decipher what “calories in” and “calories out” precisely mean, especially where the correct version could differ from the naive interpretation.
Because it seems to me that (a) the naive interpretation is wrong, but (b) most people use the “calories in, calories out” argument as if the naive interpretation is true. (“If you disagree with the naive interpretation, you ignore the laws of physics!”) Motte and bailey, etc.
Taken literally, yes. However these statements are not intended to be taken literally, they are a shorthand for “it is widely accepted that X is true, most people who deny X are either blatantly unreasonable or have strong incentives to do so. I do not expect sane people to deny X with a straight face”.
See the grandparent post. In particular, to repeat myself
In general CICO posits one-to-one correspondence between net energy balance and gaining/losing weight, regardless of anything else. This is on a time scale where short-term fluctuations (from bowel movements to water retention) are ignored as noise.
CICO also does NOT say anything about the fat/muscle ratio, it does NOT say that different foods with the same calorie content will have the same effect on weight (food you eat generally affects both the CI and the CO parts), it does NOT say that specific levels of CI (e.g. 1000 calories/day) will result in specific gain/loss of weight.
Well, I’d generally never let two strawmen fight each other.