Isn't it simply a matter of physics?

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/ ?

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!

According to Lyle McDonald, no one has ever demonstrated metabolic adaptation sufficient to eliminate weight loss when eating at a consistent deficit.

Interesting. Perhaps we should have a fund to get "stalled" people to have their BMR measured.

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.

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.

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.

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.

Here's the maths:

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.

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?

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."

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.

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 link is above, you can download the model and it is validated against published studies. http://bwsimulator.niddk.nih.gov/

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 !!

It really is simple. Most of the forum issues only dwell on the fluctuations.

One quick question:
How are you planning to do this?

How is he planning to do what?

I looked at the simulator, and it is still based on estimates.

Of course it is, everything works with estimates or correlations of physical properties etc.

The test of any simulation is if it can predict the past, which this one doesn't do too badly at - especially as the BMR equations it starts from are as you say estimates.

Isn't it simply a matter of physics?

Yes.

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.

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!).

It wasn't water weight, when I went off, I didn't lose a lot, I was just able to lose past that point. Plus, you would think that if it was just water retention, I would have shot up as I retained water, but then linearly made progress from that point. Which was not the case, although I stuck to it for 4 months hoping it was just water lol

She does take placebos one week out of four. Many BC packs have an extra week that are basically sugar pills (some have an iron supplement) because most people find it easier to maintain a habit when done every day... however, the body needs to cycle, so the placebos allow that.