> 1. You lose weight by eating less calories than your body uses. (As a corollary, you almost definitely consume more calories than you think you do. Get a calorie-counting app.)
If this is true, why don't we become incredibly fat or skinny over time? It would require incredible precision to maintain weight. But a lot of people seem to be able to do it with no effort...
The reason why this is not true is simple: our organism is not a closed system, so this thermodynamics truism does not apply. We are able, for example, to excrete nutrients without digesting them. Our organism is way too complex for this bromide to have any merit.
If this is true, why don't we become incredibly fat or skinny over time? It would require incredible precision to maintain weight. But a lot of people seem to be able to do it with no effort...
Because the amount you require for maintenance is proportional to your bodyweight. If you eat more than you need, you become fatter. As you become fatter, the amount of calories you need for maintenance goes up as well.
That's all true, but still irrelevant to the question of fixing the obesity epidemic.
"Calories eaten per day" is not a free variable. It's governed by a control loop within the brain. In a healthy person, appetite adjusts to compensate for calorie surplus or deficit. We have an epidemic because that control loop is getting damaged. People have a hard time discussing this because they treat it as a moral issue. But it's clear that recruiting our frontal cortex to count calories should not be necessary -- every mammal needs to automatically maintain homeostasis, and does so just fine in its natural environment.
And "calories burned per lb bodyweight" is also not a simple constant. It has been observed swinging significantly. A starving person's metabolism will slow dramatically to conserve energy. An overfed (healthy) person's metabolism will ramp up and favor burning the excess over storing it.
So of course we can't cheat thermodynamics, and of course eating less matters. But how to eat less is an animal behavioral question, governed by biochemistry.
Your theories about other mammals are utterly wrong - many mammals get fat in the summer and come close to starving during the winter.
As for the rest of your post, I'm not sure what you are trying to say. The human brain is made of biochemistry, so therefore choosing to eat less is a biochemistry problem? Um, sure, I guess.
The Harris-Benedict study is from 1919 on a population of 239 subjects . I'm just wondering - Do you know if it has been re-evaluated in more recent years, and was found valid?
Last time I looked into it was a years back when I had access to a university library. I dug up a couple of textbooks on sports medicine, they all generally agreed that Harris-Benedict was a good first order approximation.
In practice, it's good enough for a fat guy trying to get thin. It might not be good enough for a heavyweight trying to get down to cruiserweight without losing strength.
> "If this is true, why don't we become incredibly fat or skinny over time?"
I mean, we do. One of the big tricks here is that your basal metabolic rate is not a constant. As your weight increases you burn more energy than before simply existing. If you're running a very slight caloric surplus this will be neutralized as your weight increases, thus stabilizing you.
We do become incredibly fat or incredibly skinny over time. Or our diets change at various points, changing the net trend at times, and our weights fluctuate around a mean.
The degree of "incredible precision" it takes to maintain weight is akin to the incredible precision it takes to ride a bike, a.k.a. not particularly incredible but challenging to some.
Also a 1000 calories of sugar are going to do far different things to your body than a 1000 calories of protein. That's why focusing on calories always seemed to be the wrong metric to me.
If you mean "far different things" relating to weight gain or loss, I completely, completely disagree.
In terms of weight gain or loss, a calorie is a calorie is a calorie. That's why there are fad diets that have and do work for people that each cut different things. Low carbs in one. Low protein in another. The Cookie Diet for chrissakes. They work because the common thread between them is caloric restriction.
Now, if you consume nothing but 2000 calories of Ice Cream every day, you will surely develop some nutritional issues. And yes that totally will affect your overall health. But that's something different than what the GP was discussing (though that may well have been your entire point which is fair.)
One interesting thing I picked up from a Pollan talk on NPR (but have not yet read the underlying research myself) is that there is some evidence that in one way all calories are not the same: The mechanics of digestion is affected by the texture and composition of the food. So 100 calories of crunch granola seems to be metabolized differently than 100 calories of soft chewy brownie. But the affect here is how many calories are extracted from the input.
My source for this is a lot of reading and my own personal experiences going from 6'2, 210 and flabby to 170 and toned, cutting down from 36" waist to 32", from XL shirts to Medium in the process. I did this primarily over 14 months and did quite a bit of experimentation in there (Fruit cleanses, Juice cleanses, egg white protein supplements -- as i'm not a fan of protein powders), and for the 6 months since, as I've maintained weight and increased muscle tone.
The composition of my diet has changed but the pattern has held the same and I believe the pattern is what has had the most effect for me. Without realizing it, I devised a diet that other people call "intermittent fasting." I consume, literally, 95% of my calories in 6 hours between 2PM and 8PM (when I have my lunch, dinner and dessert). I had no idea that this was a "thing" and not just something peculiar to myself. It works beautifully for me. I gym in the morning 3 days a week. I feel healthy and skinny and look good in tight clothing and finally, finally at age 30 feel good about myself physically.
There are a lot of skinny people out there with rubbish diets, packed with carbs and low in protein.... while carbs undeniably cause hunger compared to fats and protein, there is definitely an individual variation in appetite that diet cannot completely make up for.
I was one of those hyper skinny people. There are only two reasons for it: 1) a temporarily very high metabolism that will fade with age 2) how many calories being consumed in relation to how fast your body burns
I couldn't gain a pound of weight no matter how much crap I ate, right up to about the age of 25. So I ate anything at any time, all the time. I then proceeded to gradually gain 40 pounds over seven years, from 150 to 190 (at a 6'2" height), as my metabolism slowed.
I lived off of sugar, all the time. And pasta carbs.
You'll find that some of the formerly skinny types that keep up that rubbish diet, will end up remaining slightly thinner than most except for some out-of-place looking weight gain in the mid section. That's the lucky scenario. The unlucky scenario is you give yourself diabetes or your metabolism really lets out and you just explode to twice your size.
I don't know if you've visited r/fitness or r/gainit, but metabolism really only accounts for a variance in about 200 calories. The big thing holding skinny people back is that they pretty much aren't eating enough of the good stuff - sure a skinny person might eat 3 cheeseburgers in a sitting but it doesn't help that their only exercise is cardio, or that it's the only substantial thing they actually eat all day. Many self professed skinnyfat people who claim they eat like a horse are shocked to find that they aren't consuming nearly as much calories as they think they are when it's all being tracked.
Did you actually religiously track your calories in/out?
You'll find that some of the formerly skinny types that keep up that rubbish diet, will end up remaining slightly thinner than most except for some out-of-place looking weight gain in the mid section. That's the lucky scenario.
The out of place weight gain in the mid section is actually a really good warning of future heart problem. So even that lucky scenario is not as lucky as it appears.
Because, the amount of calories your body uses is affected by your metabolism level, which is in turn affected by what you put into your body, and when you put them in. Metabolism is also affected by physical activity, but physical activity is not the only thing that affects metabolism. Finally, genetics can also affect your metabolism.
I gained 3 stone over a long time simply eating a very small surplus (50 calories a day) over a long time. People are -generally- good at eating the right amount of maintain their weight, but even a tiny margin over a long time can add up. Overweight people I know don't actually eat that much more than your average person!
Oh, and I lost that weight and more simply by - duh - eating less than my body needed. It's not an exact science, but it does work. If you don't think it does, you either have a very rare medical condition, or (sorry for the tough news) just need to eat less and exercise more, like everybody else.
If this is true, why don't we become incredibly fat or skinny over time? It would require incredible precision to maintain weight. But a lot of people seem to be able to do it with no effort...
The reason why this is not true is simple: our organism is not a closed system, so this thermodynamics truism does not apply. We are able, for example, to excrete nutrients without digesting them. Our organism is way too complex for this bromide to have any merit.