Isn't it simply a matter of physics?
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rmalford
Posts: 58
Granted, many have very limited knowledge of thermodynamics or physics, which suggests they rely on those that do. Briefly, physics is the study of how things work and to seek the fewest collection of " laws" that explain nature. Clearly some things are not covered by physics but many things are.
One of the oldest observations, or laws, is the "conservation of energy". This states the energy is neither created or lost, it only changes form. This has been repeatedly confirmed, and in fact never broken.
A calorie is a measure of energy. When fuel is burned, energy is converted to work, such as moving a mass, pumping a fluid, heating a body etc. Fueling our body requires some energy every day, say 2000C. The fuel source is generally sugars in our system or convered from fats where sugars, carbohydrates, are stored. Under normal conditions we consume energy, food, during the day convert what we need to energy and store the excess as fat.
Consume more energy and is used and it is stored. Consume less or use more energy, exercise, you must convert stored energy and will lose stored energy.
Whether this change is reflected in your weight is easily masked by hydration levels.
Sorry if this sounds pedantic or patronizing. Seems to be a habit I have developed after 50 years in research.
Comments certainly appreciated. Good luck to all in meeting their goals!
One of the oldest observations, or laws, is the "conservation of energy". This states the energy is neither created or lost, it only changes form. This has been repeatedly confirmed, and in fact never broken.
A calorie is a measure of energy. When fuel is burned, energy is converted to work, such as moving a mass, pumping a fluid, heating a body etc. Fueling our body requires some energy every day, say 2000C. The fuel source is generally sugars in our system or convered from fats where sugars, carbohydrates, are stored. Under normal conditions we consume energy, food, during the day convert what we need to energy and store the excess as fat.
Consume more energy and is used and it is stored. Consume less or use more energy, exercise, you must convert stored energy and will lose stored energy.
Whether this change is reflected in your weight is easily masked by hydration levels.
Sorry if this sounds pedantic or patronizing. Seems to be a habit I have developed after 50 years in research.
Comments certainly appreciated. Good luck to all in meeting their goals!
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probably true, but there are more variables in the human animal than the typical system studied by physicists.
We talk on here about metabolic rate (energy burned) as if we knew it to 4 significant figures, when in fact we're using a curve fit to a population that we may not even be part of and the correlation itself had an R^2 value of 0.7 and when tested you might get 70% of people that are within 10% of the estimate, if you're lucky.
So the application of precision is a challenge. BMR should perhaps be limited to two significant figures - 1400, 1600 1700 etc to remind people how accurate it is.
Seen http://bwsimulator.niddk.nih.gov/ ?0 -
While essestially you are correct, there is also a whole hormonal aspect with hormones like insulin, leptin, gherlin and others that have adaptive responses to change in food intake. That is one of the reasons why people sometimes stall and why it can be beneficial to not set too high an eating deficit and to go back to maintenance for a week or two every 12 weeks or so.0
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This has been true in my experience. As long as Nutrition is adequate and a deficit is maintained, a "plateau" will resolve itself within a couple of weeks with a substantial reduction in weight when excess retained water is flushed from the body. It's typically worse for women, as their level of retained water naturally varies a lot with hormones, menstrual cycle, etc.
According to Lyle McDonald, no one has ever demonstrated metabolic adaptation sufficient to eliminate weight loss when eating at a consistent deficit. It would be cool if that were possible, because it would mean that that person is incapable of starving to death!0 -
I mean.. that a lot of it... but in the human body there is a lot of complex **** going on and so other factors can come into play..0
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Interesting. Perhaps we should have a fund to get "stalled" people to have their BMR measured.According to Lyle McDonald, no one has ever demonstrated metabolic adaptation sufficient to eliminate weight loss when eating at a consistent deficit.
Weight loss will certainly stop if you're frightened of going below an arbitrary number like BMR, 1200 or other magic number.
The hormones and other things adapt the calorie burn but don't break the concept of an energy balance.
I ran the bodyweight simulator for a 1,000 calorie intake deficit compared to adding 1,000 calories of exercise and the latter gave a slightly higher fat loss rate on account of higher BMR.0 -
Excerpt from an interview with hiim on the subject:
In general, it’s true that metabolic rate tends to drop more with more excessive caloric deficits (and this is true whether the effect is from eating less or exercising more); as well, people vary in how hard or fast their bodies shut down. Women’s bodies tend to shut down harder and faster.
But here’s the thing: in no study I’ve ever seen has the drop in metabolic rate been sufficient to completely offset the caloric deficit. That is, say that cutting your calories by 50% per day leads to a reduction in the metabolic rate of 10%. Starvation mode you say. Well, yes. But you still have a 40% daily deficit.
In one of the all-time classic studies (the Minnesota semi-starvation study), men were put on 50% of their maintenance calories for 6 months. It measured the largest reduction in metabolic rate I’ve ever seen, something like 40% below baseline. Yet at no point did the men stop losing fat until they hit 5% body fat at the end of the study.
Other studies, where people are put on strictly controlled diets have never, to my knowledge, failed to acknowledge weight or fat loss.
This goes back to the under-reporting intake issue mentioned above. I suspect that the people who say, “I’m eating 800 calories per day and not losing weight; it must be a starvation response” are actually eating far more than that and misreporting or underestimating it. Because no controlled study that I’m aware of has ever found such an occurrence.0 -
My BMR is estimated to be around 2339 Calories or so. I did a rather rough-and-ready calculation using Newton's law of cooling and worked out that my mass required a minimum of 1700 calories per day just to maintain body temperature (if my surroundings are always at room temperature). I need to emphasise, this 1700 calories per day is for MY amount of mass (122kg) JUST to maintain body temperature. It does not include the amount of energy required for the heart to pump or the diaphragm to facilitate breathing. That's almost three quarters, nearly 75%, of my BMR is JUST to maintain body temperature! That leaves 639 calories for my heart and lungs (and any other essential life processes). 639 calories really is not a lot, but it seems like a reasonable amount for my other essential body functions.
EVEN if you discard those other functions and just consider heat, if I eat less than 1700 calories per day, for me, I CANNOT possibly gain weight or maintain weight. My body MUST use fuel already stored in my body as fat. If it did not, my body would cool to the same temperature as the surroundings and death would introduce himself. Just in terms of the physics of my body temperature, if I eat less than 1700 I CANNOT gain weight or maintain weight. FACT.
Now, I do not know if there will be some slow-down of my metabolism, but the effect of that would be fatigue, (both mental and physical)... not weight gain.
Let's not forget those 639 calories left over from my BMR. They make my target calorie intake according to MFP less than my BMR, and that is fine. That is not something I'm worried about. I shall not deliberately eat up to my BMR, there is no need, I have plenty of energy stored in my fat to keep me going. That's why I'm on this eating plan... to burn the fat: to lose weight!
If anyone is interested I'll see if I can dig out the maths for Newton's law of cooling, but it's easily findable online.0 -
Granted, many have very limited knowledge of thermodynamics or physics, which suggests they rely on those that do. Briefly, physics is the study of how things work and to seek the fewest collection of " laws" that explain nature. Clearly some things are not covered by physics but many things are.
One of the oldest observations, or laws, is the "conservation of energy". This states the energy is neither created or lost, it only changes form. This has been repeatedly confirmed, and in fact never broken.
A calorie is a measure of energy. When fuel is burned, energy is converted to work, such as moving a mass, pumping a fluid, heating a body etc. Fueling our body requires some energy every day, say 2000C. The fuel source is generally sugars in our system or convered from fats where sugars, carbohydrates, are stored. Under normal conditions we consume energy, food, during the day convert what we need to energy and store the excess as fat.
Consume more energy and is used and it is stored. Consume less or use more energy, exercise, you must convert stored energy and will lose stored energy.
Whether this change is reflected in your weight is easily masked by hydration levels.
Sorry if this sounds pedantic or patronizing. Seems to be a habit I have developed after 50 years in research.
Comments certainly appreciated. Good luck to all in meeting their goals!
Not sure what your point is.
I am going to guess you are stating in a more elaborate way the "calories in, calories out" premise.
In any case, I agree in general with you, it is a matter of physics,
As a researcher yourself, I am sure you constantly the problem of finding out the model of a particular process, etc.
The results of your model, will only be as good as the model itself.
In the case of the human digestive system, there have been attempts at modeling it, but as far as I know there is no model out there where you could just "plug-in" certain inputs, and know how many calories are consumed, how many used, etc etc and predict with certainty the result weight change.
The effort of coming up with a precise model is useless, if you consider the fact that for the food we eat, we don't have a completely precise way of measuring its effects in the body, or even if we knew it would be extremely difficult for the average person to keep track of this.
There is also uncertainty and errors on the number of calories burned during normal activities and exercise.
So the best we can do is approximations.
And there is where MFP excels !!0 -
If anyone is interested I'll see if I can dig out the maths for Newton's law of cooling, but it's easily findable online.
Some of the BMR equations use body surface area, in a similar approach.
The brain uses 400 - 600 calories, some of which will appear as heat I guess.0 -
The link is above, you can download the model and it is validated against published studies. http://bwsimulator.niddk.nih.gov/In the case of the human digestive system, there have been attempts at modeling it, but as far as I know there is no model out there where you could just "plug-in" certain inputs, and know how many calories are consumed, how many used, etc etc and predict with certainty the result weight change.0 -
Here's the maths:If anyone is interested I'll see if I can dig out the maths for Newton's law of cooling, but it's easily findable online.
The mean specific heat capacity of the human body is 3500J/kgK, so at about 122kg that is 427kJ/K. Newton's law of cooling is T(t) = T_e + (T_0 - T_e)e^(-kt) where T(t) is the temperature after a time t, T_e is the temperature of the surrounding environment, T_0 is the initial temperature, t is the time that has expired and k is a constant that depends on the material of the body. For the human body I have calculated k=0.135 (per hour), so within 24 hours we can work out how the temperature of a body would drop without the body's metabolism keeping it warm.
T = 20 + (37.5 - 20)e^(-24 * 0.135)
T = 20.69
So the difference in temperature over 24 hours is 16.8 °C, which means 7.17 MJ of energy per day (minimum estimate) just for maintaining the body temperature. 1MJ = 239 calories so 7.17 MJ = 1700 calories (2sf) per day just for maintaining body temperature.0 -
Plus, most of us don't base our eating decisions on math and physics -- there are tons of social, emotional and mental issues as well. So, just because I KNOW certain eating patterns are bad for me, maybe I choose that anyway because of habits, because all my friends are doing it, because for my whole life I've coped with stress/anxiety/boredom etc. by eating a certain way. You can eat a very restricted diet, and lose a bunch of weight, but if you haven't addressed the other issues, the habits and patterns that got you in trouble in the first place are still there, and since you've dropped your metabolic rate, the weight comes right back.
So, no,humans being human, it's NOT just a matter of physics.
In those studies -- how were all these people doing a year after they finished?0 -
This is true. Level of fitness (or fatness) is the product of lifestyle over time. If people diet, rather than changing their lifestyle, as soon as their routine goes back to what it was before, their results will go back to what they were before. But this doesn't really have anything to do with "starvation mode."Plus, most of us don't base our eating decisions on math and physics -- there are tons of social, emotional and mental issues as well. So, just because I KNOW certain eating patterns are bad for me, maybe I choose that anyway because of habits, because all my friends are doing it, because for my whole life I've coped with stress/anxiety/boredom etc. by eating a certain way. You can eat a very restricted diet, and lose a bunch of weight, but if you haven't addressed the other issues, the habits and patterns that got you in trouble in the first place are still there, and since you've dropped your metabolic rate, the weight comes right back.
So, no,humans being human, it's NOT just a matter of physics.
In those studies -- how were all these people doing a year after they finished?0 -
Sort of makes using MFP pointless then.Plus, most of us don't base our eating decisions on math0 -
Excerpt from an interview with hiim on the subject:
In general, it’s true that metabolic rate tends to drop more with more excessive caloric deficits (and this is true whether the effect is from eating less or exercising more); as well, people vary in how hard or fast their bodies shut down. Women’s bodies tend to shut down harder and faster.
But here’s the thing: in no study I’ve ever seen has the drop in metabolic rate been sufficient to completely offset the caloric deficit. That is, say that cutting your calories by 50% per day leads to a reduction in the metabolic rate of 10%. Starvation mode you say. Well, yes. But you still have a 40% daily deficit.
In one of the all-time classic studies (the Minnesota semi-starvation study), men were put on 50% of their maintenance calories for 6 months. It measured the largest reduction in metabolic rate I’ve ever seen, something like 40% below baseline. Yet at no point did the men stop losing fat until they hit 5% body fat at the end of the study.
Other studies, where people are put on strictly controlled diets have never, to my knowledge, failed to acknowledge weight or fat loss.
This goes back to the under-reporting intake issue mentioned above. I suspect that the people who say, “I’m eating 800 calories per day and not losing weight; it must be a starvation response” are actually eating far more than that and misreporting or underestimating it. Because no controlled study that I’m aware of has ever found such an occurrence.
Yeah, I think of this every time I see a "OMG I EAT 1200 AND DONT LOSE WEIGHT!" post. I suspect that the reason eat more to lose more works is that when people are allowed a higher allowance there is less "I'm embarrassed of this so I'm not going to log just this one thing" or "Sure, this baseball sized serving of peanut butter is gonna be 2 tbls."
I would say, though, that it is not entirely simple math. 4 months in (like 20 pounds lost or so) I went on birth control. Kept doing the same things, could only lose a pound a month and that only came off during the placebo pills. And was starving all the time, still doing exactly what I had been successful and not deprived with before. I tried eating less for a few weeks, eating more for a few weeks, damn scale wouldn't move. Bought a bodybugg so I could better keep track of the calories out side of the equation, for two months ate ~500 less than what it said, still no loss. Went off the pill and suddenly the ~500 deficit equaled damn near a pound a week. Hormones make the body too complex for the simple calories in calories out model. However, I think it is true most of the time
Hope the girly stuff made all you boys cringe.0 -
One of the really neat things about physical systems is it really doesn't matter whether or not one believes it!
Yes it is simply calories in vs calories out. The beauty of fundamental laws is you don't need to understand every detail (calories burned, calories in, phase of the moon etc) you can still make certain predictions. My "point" is if you eat fewer calories than you burn, you will lose weight, at least until you starve to death. Water, added muscle,and various phase of the moon effects can introduce weight fluctuations, but over time the energy deficit will have to be filled.
It really is simple. Most of the forum issues only dwell on the fluctuations.0 -
The link is above, you can download the model and it is validated against published studies. http://bwsimulator.niddk.nih.gov/In the case of the human digestive system, there have been attempts at modeling it, but as far as I know there is no model out there where you could just "plug-in" certain inputs, and know how many calories are consumed, how many used, etc etc and predict with certainty the result weight change.
I looked at the simulator, and it is still based on estimates.
As I pointed out on my post, even if we had the perfect simulator, it would be so complex that it would be not usable by the regular person. I bet not even by the researchers that would come up with that model ! :bigsmile:
My main point: We don't need an exact model. The approximations that MFP provides are good enough as a starting point; and from there on, each individual can make corrections and adjustments, depending on what works for each.
Really, no need for thermodynamics or complex math !!0 -
One of the really neat things about physical systems is it really doesn't matter whether or not one believes it!
Yes it is simply calories in vs calories out. The beauty of fundamental laws is you don't need to understand every detail (calories burned, calories in, phase of the moon etc) you can still make certain predictions. My "point" is if you eat fewer calories than you burn, you will lose weight, at least until you starve to death. Water, added muscle,and various phase of the moon effects can introduce weight fluctuations, but over time the energy deficit will have to be filled.
It really is simple. Most of the forum issues only dwell on the fluctuations.
One quick question:
How are you planning to do this?0 -
How is he planning to do what?
One quick question:It really is simple. Most of the forum issues only dwell on the fluctuations.
How are you planning to do this?0 -
The birth control thing would have been water retention. They mostly work by elevating estrogen/progesterone levels, which leads to some serious water retention. The fact that you didn't GAIN weight after going on them is impressive (most women pick up a couple pounds of water weight). It's definitely harder for women to get an idea of actual weight loss, which is why it's important to have a diet/exercise strategy that you know will work, and stick with it (which is sounds like is exactly what you did!).Yeah, I think of this every time I see a "OMG I EAT 1200 AND DONT LOSE WEIGHT!" post. I suspect that the reason eat more to lose more works is that when people are allowed a higher allowance there is less "I'm embarrassed of this so I'm not going to log just this one thing" or "Sure, this baseball sized serving of peanut butter is gonna be 2 tbls."
I would say, though, that it is not entirely simple math. 4 months in (like 20 pounds lost or so) I went on birth control. Kept doing the same things, could only lose a pound a month and that only came off during the placebo pills. And was starving all the time, still doing exactly what I had been successful and not deprived with before. I tried eating less for a few weeks, eating more for a few weeks, damn scale wouldn't move. Bought a bodybugg so I could better keep track of the calories out side of the equation, for two months ate ~500 less than what it said, still no loss. Went off the pill and suddenly the ~500 deficit equaled damn near a pound a week. Hormones make the body too complex for the simple calories in calories out model. However, I think it is true most of the time
Hope the girly stuff made all you boys cringe.0
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