the 3,500 cal = 1 lb rule

You've stumbled on one of the basic streamlines of nutrition. The efficiency of food digestion and absorption, the caloric density of fat cells, thermogenesis, metobalic expenidture. etc. all make calorie counting a inexact activity. But while the numbers do vary, the philosophy is sound and you can attain your goals. Just remember, your body is not an exact machine. Its like a pendulum in its responses, swinging outside of the norm occasionally but usually ending up in the right place for the stimuli in the long run.

I've always gone with 3600 cal/lb in my calcultions, but that is what I was taught many years ago.

Interesting.

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... It's estimated the average American eats about 300 excess calories a day but the average American only gains .75 lbs per year. The 3,500 rule says that 300 calories a day should result in 31 lbs per year so that's a 4,100% margin of error!

The reality is we don't have a mathematical model that explains obesity because the issue is far more complex than most people take it for. ...

Very interesting indeed. There's a lot more to this dieting than meets the eye. It just goes to prove that you have a fairly big window to aim at, if you have a lot to lose. Once you get down to the final pounds, recompositioning, gaining, etc, there's a good chance that you know a lot more about how your body deals with its nutrients, albeit probably instinctively rather than rationally. I've been logging accurately for basically a year, from fat to fit, and I don't really know what goes on. I seem to maintain my weight at anywhere between 1900 and 2400 calories.

(Edit - 'it's')

There will always be a margin for error in any sweeping statement like that.

I dealt extensively with animal feed nutrition at college and all individuals have a varying FCR (feed conversion ratio) - the point is, it gives you an approximation to start off with. You may find that through experimentation you convert feed more or less efficiently than that. Of course, the nutritional components of your food will have a bearing.

Also - calorific values for foodstuffs are obtained by bomb calorimitry, and bodies are not bomb calorimiters and do not utilise 100% of the available energy in a food source. Again, calorific yields should be used as a guide, as you are putting them all through the same machine (your body), and you can, by experimentation, tweak accordingly.

basically this is saying that it isn't a hard and fast rule and more of a generality...which is true. nobody has a TDEE of exactly XXXX calories...I've been maintaining for over a year now and I have a variable range of calories for which I maintain my weight. That said, the 3500 calorie generality works...there of course is a margin of error, but it works, particularly as a good starting point. as with anything, adjustments must be made per real world results. there are no hard and fast rules when it comes to this stuff.

as you stated, you have to trust the overall process.

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It's all approximate. But it's still a reasonable approach of weight loss. If you don't lose fast enough, you can always adjust your goal to make it work for you, but at least you have a base to lean yourself on... Otherwise it would be 100% guesswork.

You and I differ on what's reasonable. I can't say employing a method that might not work at all is reasonable.

Trial and error isn't 100% guess work. For example, we know that a big part of losing weight is eating less calories right? So if someone were to figure out how much they currently eat per day and drop that by 500 calories is that guess work? Repeat the process until you get the weight loss results you desire and now that's a solid process.

The problem with saying "this calculation works" when it really doesn't is that people (and literally millions of them) hop onto forums and say things like "I'm eating at a deficit and I'm not losing weight" or "I'm eating what I'm supposed to and not losing weight". Basically these are people who put trust in the calculations over a process, and as long as we tout the calculations as accurate people will fall into this trap.

If we were to ditch the calculations and call them completely unreliable as they are then people are forced to stick to a process which is close to fail proof (there are exceptions to every rule of course though). Point is people will be better off without them and it's not guessing it's a process.

Those people are estimating wrong though. They don't weigh their food or don't log properly and underestimate their calorie intake... or overestimate their exercise calories... so of course they're not losing weight.

For your 4,100% margin of error, well, it was a pretty vague statement to start with... ' It's estimated the average American eats about 300 excess calories a day but the average American only gains .75 lbs per year'... that doesn't mean anything, and heck, I'd say it's pretty impossible quite frankly. Where do you even get those numbers from?

Margin of error on the 3500 cal = 1 lb rule is probably w-a-a-a-a-y less than the margin of error on the nutrient percentages of your food. There's no way it can be an exact process in real world conditions.

The margin of error on the whole 3,500 cal = 1 lb is about 30%. Adipose tissue isn't all fat, it's actually only about 60% - 85% fat. If you do the math on a straight up pound of fat you get 453g * 9C/g = 4077C. Take 85% of that and you get 3465 which is how we get roughly 3,500C per pound of fat; however, it's as little as 60% fat so that means it could be as little as 2,500 calories stored in a pound of fat.

Now when we talk about net calories (a.k.a. how many calories we actually get from the gross calories we ingest) the margin of error for conversion to fat is huge! In the laws of thermodynamics calories in versus calories out is a gross over simplification that ignores many aspects. The laws as it applies to digestion are more like this:

calories in = BMR + activity + entropy + energy transfer + changes in fat stores

Now we only control 2 of the 6 variables to balance the equation for the conservation of energy. That means our body can easily autonomously adjust the others to balance the equation without ever touching fat stores.

When you look at American eating habits this is very obvious. It's estimated the average American eats about 300 excess calories a day but the average American only gains .75 lbs per year. The 3,500 rule says that 300 calories a day should result in 31 lbs per year so that's a 4,100% margin of error!

The reality is we don't have a mathematical model that explains obesity because the issue is far more complex than most people take it for. Recently the NIH funded a team to try to come up with a more accurate model and while they determined the 3,500 rule is false their model still doesn't explain the trends in obesity well either. I have to say though the new model is much closer...

At any rate, without accurate mathematical models we cannot say with any certainty the formulas we are using are useful at all.

Well, you made a few assumptions which are widely off the mark that are misleading, even though in general there are definitely not well understood variables involved. Yes fat tissue is made of other than just fat, but, we don't generally lose the cellular tissue or cells, just contents of the cells. In fact most times in weight loss you lose little to NO other tissue other than fat content in the cells: they shrink and enlarge based on whats inside them. So this first "controversy" is not really existent in most cases of weight loss and can generally be ignored.

We also cannot say you eat to x calories excess, so you gain x/3500 calories of pounds. We don't all absorb all energy sources to the same extent, our efficiency at it is different dependent on the substrate and the digestion and while in a surplus the body does not absorb as high of a percent of the calories, naturally this declines as you increase. So, there goes almost your whole 4100% variable, it just doesn't happen that way when the body does not absorb all the calories, so they never make it into the system to make such a variable.

Now, the case of losing weight to adding a few 100 calories and gaining is completely different, because your body is not in a "I have all these excess calories every day that I don't need" state, its in a "I've not had enough calories to refill my muscle and fat energy stores in a long while, and now I can!" state. You can see how that is different.

However, yes there are still huge variables including metabolic rate, digestion, absorption and intestinal bacterial effects on each food, and the body's efficiency in regulating absorption. You just can't know the exact set point of all your personal factors at this point, so it takes some "experimentation" for each individual in losing weight and "adjustment". Then maintaining is a whole separate ball of wax and again is not purely calories in vs calories out because of the way the body adjusts and reacts to what its "set point" naturally is.

Even with all the factors of uncertainty, you STILL can best simplify weight loss to calories in vs calories out and make adjustments depending on the factors you don't know. This is the most logical and appropriate method to first take, since intake truely is the biggest manageable variable, then fine tune depending on what you see for results over time.

Hmm, you posted this as a kind of "refuting" of what I said but none of your statements do, maybe clarification is in order. Not trying to be mean, just trying to clear the air.

Yes fat tissue is made of other than just fat, but, we don't generally lose the cellular tissue or cells, just contents of the cells. In fact most times in weight loss you lose little to NO other tissue other than fat content in the cells: they shrink and enlarge based on whats inside them. So this first "controversy" is not really existent in most cases of weight loss and can generally be ignored.

So you're suggesting that a fat cell which contains 30% water will keep that 30% water when the actual fat is depleted? Sorry but that's not true. When fat is mobilized for energy consumption nothing I've ever read suggests that the water will remain. One of the reasons why it's likely fat contains water in the cell is that water is needed for fat mobilization.

Who said anything about water balance? I was saying only that the calculation for a pound you went through is off because the cells do not lose the protein structures at a rate that was significant when fat stores are used up, and you can essentially ignore the "controversy" you stated that fat cells are not all fat.

Addressing the off target water answer, one of the theories is that fat cells take on water as they lose contents, that does suggest water remains however, and is part of the "discrepancy in weight loss", showing they may take on water before shrinkage and the scale doesn't move for a while (further taking away strength from the 3500 cals does not equal a pound argument), but that was not what I was saying at that point and I'm confused why water is being talked about here. The point is in losing weight, 3500 calories of fat to a pound is a great approximation, not a bad one because only 60+% of a fat cell is made up of fat, (as you suggested).

We also cannot say you eat to x calories excess, so you gain x/3500 calories of pounds. We don't all absorb all energy sources to the same extent, our efficiency at it is different dependent on the substrate and the digestion and while in a surplus the body does not absorb as high of a percent of the calories, naturally this declines as you increase. So, there goes almost your whole 4100% variable, it just doesn't happen that way when the body does not absorb all the calories, so they never make it into the system to make such a variable.

I've clearly distinguished net calories from gross calories in the discussions. If you don't know entropy is the efficiency of a system so this includes things like TEF for digestion. Energy transfer accounts for the rest which is energy that doesn't make it into the system (i.e. bits of undigested nuts/seeds in your BMs). The problem with calories in versus calories out is it doesn't account for either, so that means the 4,100% is quite relevant.

Entropy was not brought up and was violated only by your 4100% statement, not mine. It is clearly conserved in what I said: if not all calories are efficiently absorbed, ingestion of them does not mean they enter the system (person) but go right on through, bacteria eat some, some is undigested. The body controls some of what is absorbed based on needs. So no, you cannot say "you ate it, so its now absorbed", which means the 4,100% is very imaginary and not helpful. What you say above also shows the 4100% is not true since you also admit to in your words TEF for digestion and some energy doesn't make it into the system.

I think you are actually kind of agreeing with what I say here and just not acknowledging those factors really disrupt that 4100% claim extremely I'm obviously not arguing the factors change, but that because they change, there is no 4,100% difference in calories to weight gain conversion, it is a false construct, especially when a lot of it doesnt even get into the system.

Now, the case of losing weight to adding a few 100 calories and gaining is completely different, because your body is not in a "I have all these excess calories every day that I don't need" state, its in a "I've not had enough calories to refill my muscle and fat energy stores in a long while, and now I can!" state. You can see how that is different.

Except the body is often in a "I have all these excess calories every day that I don't need" because of how much people grossly overeat. It's exactly why the body increases BMR, entropy, and energy transfer in the presence of gross caloric over consumption. This is easily observed when you get flush from eating a large carbohydrate based meal. Basically the body cannot process all the extra carbohydrates so it uses something called the futile cycle to burn off extra carbs via heat generation. Consequently this is also notable in severe caloric deprivation because heart rate and body heat both drop - signs the body is trying to conserve more energy.

You are actually agreeing with what I said here. The body adjusts factors it can in digestion, absorption and efficiency, and the state which is more common (excess) causes the body to adjust factors it can for absorption down and use up, which is very different from the state of going from a dearth to a small increase. Dearth to small increase sees good utilization and storage of these calories, resulting in a small intake going quickly to perceived weight gain.

Even with all the factors of uncertainty, you STILL can best simplify weight loss to calories in vs calories out and make adjustments depending on the factors you don't know. This is the most logical and appropriate method to first take, since intake truely is the biggest manageable variable, then fine tune depending on what you see for results over time.

To a certain extent I agree, but my overall point remains that it's the adjustments part that matters the most not the base calculations. Hence why we can literally just throw out the calculations and recommend a process based approach starting with current intake. That way people don't say things like "I'm eating at a deficit and not losing weight" which is an impossible condition.

You are actually agreeing with me here again?

*edited for the left out question mark and for further comments: it sounds like you are really just coming from this from a slightly different direction. I just would say current intake probably a bigger unknown than anything else, otherwise they wouldnt have gotten so overweight. Calories just seems the best way to be aware, time and time again I find people doing the "its healthy, so its OK" error, forgetting calories, then when its calculated...oops...you overate again.

Currently, there’s no way to determine how much energy an individual actually obtains from 1 g of carbohydrate, protein, or fat.

Doesn't a metabolic chamber do that ? With measured airflow, analysis and temperatures plus urine and faeces analysis you can make some attempt at measuring what came out of the amount of food that went in.

A metabolic chamber could tell how much carbohydrates or fat a person is using, but not how much they got from their gross intake. Fecal analysis can help determine nitrogen retention, but doesn't necessarily tell you how much protein is converted to glucose via gluconeogenesis or used for muscle development/repair. Neither of these processes tells you what the energy is expended on. So let's say I can tell I'm burning 2,000 calories there's no way to tell what this is being spent on. So that could be 1,000 for digestion and 500 for organs and 500 for immune system or 1,000 for organs 800 for immune system and 200 for digestion.

Not sure I understand what you mean by "got" or "spent on". If you know the food intake and the waste output, didn't you "get" the rest ?