The calories-in calories-out model is attractive, but it doesn’t appear to be all that accurate, or at least it’s incomplete. The body responds differently to different foods. They might have different effects on various hormones (e.g. the ones that regulate hunger), and they might be broken down and redistributed in different ways. In one study (Kekwick and Pawan), three groups of people were put on 1,000 calorie diets of 90% fat resp. 90% protein resp. 90% carbs. The first group lost 0.9 lbs / day, the second group lost 0.6 lbs / day, and the third group gained 0.24 lbs / day. (I don’t know to what extent the study controlled for exercise but I think it’s safe to assume that the difference in the amount of exercise that each group did wasn’t large enough to explain these results.) As Tim Ferriss puts it in The 4-Hour Body:
The creator of the “calorie” as we know it, 19th-century chemist Wilbur Olin Atwater, did not have the technology that we have today. He incinerated foods. Incineration does not equal human digestion; eating a fireplace log will not store the same number of calories as burning one will produce. Tummies have trouble with bark, as they do with many things.
In the context of solving the specific problem of fat loss, one goal is not to lose muscle, and what you’re eating should affect how easy it is to target fat and retain muscle as well.
And, of course, diets don’t work if they can’t be maintained. The fact that different foods affect the hormones that regulate hunger differently (some foods even make you hungrier!) means that different diets, even with the same number of calories, require different amounts of willpower to maintain.
I’m heartened that your comment is so well-liked. I made the same point a year or two ago and got back a bunch of nonsense about how the second law of thermodynamics cannot be violated.
It’s interesting that the second law of thermodynamics is what people use here. As long as your metric is losing weight, the relevant physical law is conservation of mass, and starting from conservation of mass helps clarify the issue enormously, I think. (Apparently the mechanism by which burning calories actually causes you to lose weight is exhalation of carbon dioxide. I feel like I knew this once, but forgot and only very recently relearned it.)
Carbon Dioxide and water are the two main byproducts of fat metabolism, which made me really happy to learn because it basically killed my worries about focusing on bowel movements. You literally can sweat the fat away!
Indeed not from burning calories, sorry. However, it still has to be subtracted from the intake, just like the amount you exhale, so reducing absorption is just as important as increasing burning.
Actually, I could not find any data online on the food energy utilization in the small intestine in humans and on the factors affecting it. Apparently the obvious ways to prevent absorption, like laxatives, don’t really work in the long term.
I don’t think so, because calories are a unit of energy, so a simple calories-in calories-out model would necessarily model energy balance as energy intake (through food) and energy expenditure (through body maintenance and activity). Your thermodynamic/energy balance is what would ultimately determine either the anabolism or catabolism of different tissues (a more complex calories-in calories-out model, rather than the simpler one mentioned, would have the greatest explanatory power, I imagine. Metabolic rate is under hormonal control, hormones interact in complex ways, and intake of different foods and different activity patterns can alter hormone expression. A calorie-budget model incorporating varying hormone expression/sensitivity, genetics [for both little things like minute differences in receptor molecules and bigger ones like hyperthyroidism], and different metabolic pathways used [as dictated largely by the previous two], would be pretty accurate, I reckon).
Weight can also be stored as different things, which is why it’s not the best proxy for the success or failure of a “diet”. Different substances (like fat or muscle or glycogen or water) have different energy densities, so not all changes in weight signify the same thing (presumably, a “dieter” wants to lose fat. Drinking a gallon of water might cause his weight to rise beyond where it was a month ago, but that does not mean that his “diet” has been shot, or that he has gained fat). A study that looks only at weight change and not change in body composition under different conditions would enormously simplify what that weight represents—in the study Qiaochu_Yuan mentions, 90% fat diets might have gained fat and lost muscle, water, and glycogen, resulting in a net weight loss, where the 90% carbs group gained muscle, glycogen, and water, and lost fat, resulting in net weight gain. The second case is obviously preferable to “dieters” than the first.
(what I suspect happened in the study is that the first two groups were depleted of glycogen, an energy source the body tends to use before it starts catabolizing fat or muscle deposits. Glycogen also tends to increase water retention, further inflating the weight of high-carb dieters. If they put all three groups on a 0-carb diet for a week to deplete glycogen stores and then dehydrated them, I’d suspect their net weight loss to be much more similar (changes in muscle and fat would vary [again, because of hormonal interactions and different energy densities], but bodies seem to need a lot less protein for maintenance than often suggested so unless the non-protein groups were consuming mostly carbs/fats for their 10% I doubt there’d be a huge difference)(also, the fact that obese individuals might gain muscle/fat on a 1000 kcal diet is obviously silly. If they were using the [again, stupidly oversimplified] BMI to define obesity [where obesity occurs at BMIs>30], a 5′10″ man would have to weigh >209lbs, giving him a BMR at minimum of roughly between 1500 and 2000 calories, which is a good bit more than 1000kcal, so he’d still probably lose weight [but ignoring changes in BMR from hormones and such] completely sedentary)
There’s also calorie type influencing activity level (eg, People starting ketogenic diets often report lethargy that eventually levels off, but whether that’s a true return to past alertness or a subjective change in perceived vigor I’m not sure).
I don’t understand what you’re disagreeing with. Is it “as long as your metric is losing weight, the relevant physical law is conservation of mass”? Because that seems obviously true to me. What you seem to be arguing is that your metric shouldn’t be losing weight, which is reasonable, but you’re not disagreeing with me.
Huh, I think I read your comment too quickly and missed the “as long as...: qualifier and then started replying and went off on a tangent and forgot what the original comment was. Hah. My bad. Also didn’t notice your name, hence my reference to you in the 3rd person.
Yeah, weight’s not the best metric to use without taking into account body composition.
Oh wait, I think I figured it out. I’d combined your post and paper-machine’s in my head, so I thought the simple calories-out-calories-in model in the highest level post being the thing referred to by discussion of conservation laws.
I’m heartened that your comment is so well-liked. I made the same point a year or two ago and got back a bunch of nonsense about how the second law of thermodynamics cannot be violated.
I noticed the same difference in response myself and was similarly pleasantly surprised.
1,000 calorie diets …
third group gained 0.24 lbs / day
I noticed I was confused. This doesn’t seem consistent with the results of the Minnesota Starvation/Semistarvation Study. I went to Wikipedia.
Kekwick and Pawan, 1956 conducted a study of subjects consuming 1000-calorie diets, some 90% protein, some 90% fat, and some 90% carbohydrates. Those on the high fat diet lost the most, the high protein dieters lost somewhat less, and the high carbohydrate dieters actually gained weight on average.
Kekwick and Pawan noted irregularities in their study (patients not fully complying with the parameters of the study). The validity of their conclusions has been questioned, and follow-up studies over a longer duration concluded that these temporary differences were due chiefly to changes in water balance (citation)
My prior consider it quite ludicrous that you can gain weight eating at a 50% deficit, no matter what your macros. The criticisms seem reasonable enough to explain the effect.
Note that the link in the citation claimed that when told to cut out carbs and eat as much protein and fat as they liked, “In all subjects, there was a reduction in calories ranging from 13% to 55% during the time they were consuming the low-carbohydrate diet.”
So long as your diet isn’t nearly that lopsided, IME (YMMV) the calories-in calories-out is a more decent first-order approximation than many people realize. See also The Hacker’s Diet. Second-order effects exist, but they’re second-order effects.
Places way too much focus on losing weight. See parent; losing weight by losing muscle mass isn’t desirable.
Second-order effects exist, but they’re second-order effects.
Your claim here hinges on the presumption that CI and CO are the only first-order effects, which is almost certainly false. Age, body fat proportion, maximal oxygen uptake, etc., are plausible candidates that I’ve seen in mathematical weight models.
Age, body fat proportion, maximal oxygen uptake...
In my experience, these tend to be taken into effect when calculating the “calories out” part of the equation. By what mechanism were you thinking that these mattered, that’s not “calories out”?
Sure, but as you probably know, calories eaten are stored into multiple deposits, depending on various internal and external factors. If the availability of those deposits varies, it might not be so easy to deplete most of the calory intake, short of completely starving oneself.
Surely the more obvious solution is “eat less calories than you use.”
The calories-in calories-out model is attractive, but it doesn’t appear to be all that accurate, or at least it’s incomplete. The body responds differently to different foods. They might have different effects on various hormones (e.g. the ones that regulate hunger), and they might be broken down and redistributed in different ways. In one study (Kekwick and Pawan), three groups of people were put on 1,000 calorie diets of 90% fat resp. 90% protein resp. 90% carbs. The first group lost 0.9 lbs / day, the second group lost 0.6 lbs / day, and the third group gained 0.24 lbs / day. (I don’t know to what extent the study controlled for exercise but I think it’s safe to assume that the difference in the amount of exercise that each group did wasn’t large enough to explain these results.) As Tim Ferriss puts it in The 4-Hour Body:
In the context of solving the specific problem of fat loss, one goal is not to lose muscle, and what you’re eating should affect how easy it is to target fat and retain muscle as well.
And, of course, diets don’t work if they can’t be maintained. The fact that different foods affect the hormones that regulate hunger differently (some foods even make you hungrier!) means that different diets, even with the same number of calories, require different amounts of willpower to maintain.
I’m heartened that your comment is so well-liked. I made the same point a year or two ago and got back a bunch of nonsense about how the second law of thermodynamics cannot be violated.
It’s interesting that the second law of thermodynamics is what people use here. As long as your metric is losing weight, the relevant physical law is conservation of mass, and starting from conservation of mass helps clarify the issue enormously, I think. (Apparently the mechanism by which burning calories actually causes you to lose weight is exhalation of carbon dioxide. I feel like I knew this once, but forgot and only very recently relearned it.)
Probably a brain fart for the first law?
Carbon Dioxide and water are the two main byproducts of fat metabolism, which made me really happy to learn because it basically killed my worries about focusing on bowel movements. You literally can sweat the fat away!
Probably not as much as excreting all the unprocessed food from the other end.
That’s not true. Most of the material in bowel movements was never in your fat to begin with.
Indeed not from burning calories, sorry. However, it still has to be subtracted from the intake, just like the amount you exhale, so reducing absorption is just as important as increasing burning.
Is this actually true? Do you have a citation for this?
Actually, I could not find any data online on the food energy utilization in the small intestine in humans and on the factors affecting it. Apparently the obvious ways to prevent absorption, like laxatives, don’t really work in the long term.
I don’t think so, because calories are a unit of energy, so a simple calories-in calories-out model would necessarily model energy balance as energy intake (through food) and energy expenditure (through body maintenance and activity). Your thermodynamic/energy balance is what would ultimately determine either the anabolism or catabolism of different tissues (a more complex calories-in calories-out model, rather than the simpler one mentioned, would have the greatest explanatory power, I imagine. Metabolic rate is under hormonal control, hormones interact in complex ways, and intake of different foods and different activity patterns can alter hormone expression. A calorie-budget model incorporating varying hormone expression/sensitivity, genetics [for both little things like minute differences in receptor molecules and bigger ones like hyperthyroidism], and different metabolic pathways used [as dictated largely by the previous two], would be pretty accurate, I reckon).
Weight can also be stored as different things, which is why it’s not the best proxy for the success or failure of a “diet”. Different substances (like fat or muscle or glycogen or water) have different energy densities, so not all changes in weight signify the same thing (presumably, a “dieter” wants to lose fat. Drinking a gallon of water might cause his weight to rise beyond where it was a month ago, but that does not mean that his “diet” has been shot, or that he has gained fat). A study that looks only at weight change and not change in body composition under different conditions would enormously simplify what that weight represents—in the study Qiaochu_Yuan mentions, 90% fat diets might have gained fat and lost muscle, water, and glycogen, resulting in a net weight loss, where the 90% carbs group gained muscle, glycogen, and water, and lost fat, resulting in net weight gain. The second case is obviously preferable to “dieters” than the first.
(what I suspect happened in the study is that the first two groups were depleted of glycogen, an energy source the body tends to use before it starts catabolizing fat or muscle deposits. Glycogen also tends to increase water retention, further inflating the weight of high-carb dieters. If they put all three groups on a 0-carb diet for a week to deplete glycogen stores and then dehydrated them, I’d suspect their net weight loss to be much more similar (changes in muscle and fat would vary [again, because of hormonal interactions and different energy densities], but bodies seem to need a lot less protein for maintenance than often suggested so unless the non-protein groups were consuming mostly carbs/fats for their 10% I doubt there’d be a huge difference)(also, the fact that obese individuals might gain muscle/fat on a 1000 kcal diet is obviously silly. If they were using the [again, stupidly oversimplified] BMI to define obesity [where obesity occurs at BMIs>30], a 5′10″ man would have to weigh >209lbs, giving him a BMR at minimum of roughly between 1500 and 2000 calories, which is a good bit more than 1000kcal, so he’d still probably lose weight [but ignoring changes in BMR from hormones and such] completely sedentary)
There’s also calorie type influencing activity level (eg, People starting ketogenic diets often report lethargy that eventually levels off, but whether that’s a true return to past alertness or a subjective change in perceived vigor I’m not sure).
I don’t understand what you’re disagreeing with. Is it “as long as your metric is losing weight, the relevant physical law is conservation of mass”? Because that seems obviously true to me. What you seem to be arguing is that your metric shouldn’t be losing weight, which is reasonable, but you’re not disagreeing with me.
Huh, I think I read your comment too quickly and missed the “as long as...: qualifier and then started replying and went off on a tangent and forgot what the original comment was. Hah. My bad. Also didn’t notice your name, hence my reference to you in the 3rd person.
Yeah, weight’s not the best metric to use without taking into account body composition.
Oh wait, I think I figured it out. I’d combined your post and paper-machine’s in my head, so I thought the simple calories-out-calories-in model in the highest level post being the thing referred to by discussion of conservation laws.
I don’t understand what the first sentence is disagreeing with.
I noticed the same difference in response myself and was similarly pleasantly surprised.
Due to the evolution of general sensibility or the Karma power-law?
No idea. Probably just random chance. The parent of Qiaochu’s comment is now at zero, so “evolution of general sensibility” is slightly less likely.
I noticed I was confused. This doesn’t seem consistent with the results of the Minnesota Starvation/Semistarvation Study. I went to Wikipedia.
My prior consider it quite ludicrous that you can gain weight eating at a 50% deficit, no matter what your macros. The criticisms seem reasonable enough to explain the effect.
Note that the link in the citation claimed that when told to cut out carbs and eat as much protein and fat as they liked, “In all subjects, there was a reduction in calories ranging from 13% to 55% during the time they were consuming the low-carbohydrate diet.”
Thanks for looking this up! Regrettably, I did not notice that I was confused.
So long as your diet isn’t nearly that lopsided, IME (YMMV) the calories-in calories-out is a more decent first-order approximation than many people realize. See also The Hacker’s Diet. Second-order effects exist, but they’re second-order effects.
That’s basically the point.
Places way too much focus on losing weight. See parent; losing weight by losing muscle mass isn’t desirable.
Your claim here hinges on the presumption that CI and CO are the only first-order effects, which is almost certainly false. Age, body fat proportion, maximal oxygen uptake, etc., are plausible candidates that I’ve seen in mathematical weight models.
In my experience, these tend to be taken into effect when calculating the “calories out” part of the equation. By what mechanism were you thinking that these mattered, that’s not “calories out”?
Calorie use is not constant, and varies with calorie intake and type, among other things.
Sure, but as you probably know, calories eaten are stored into multiple deposits, depending on various internal and external factors. If the availability of those deposits varies, it might not be so easy to deplete most of the calory intake, short of completely starving oneself.
Plus you also have to deal with massive willpower problems.