If you eat 500 calories and burn 600 calories, the energy has to come from somewhere. So in a sense it is actually a pretty simple physics problem.
It gets tricky because calculating calorie consumption is really hard (how much of what you ate was actually turned into energy) and calculating calorie expenditure is probably even harder.
>If you eat 500 calories and burn 600 calories, the energy has to come from somewhere.
Yes, hence "you have to balance your chemical equations", but we need to agree on what we're calling "eat" and "burn", here.
Burning 600 calories can just as well "work up an appetite" as it can "draw upon fat reserves".
We're used to thinking of weight loss as a behavioral problem withy metabolic symptoms ("he eats too much, so he got fat") whereas there's reason to consider it as a metabolic problem with behavioral symptoms ("the kind of food he eats signals to the body that fat should be created, so his body signals for him to eat more").
I've yet to meet a fat person who didn't eat large portions and sugary foods.
"It's a glandular problem," you'd often hear a few decades back. Now, there is other mumbo-jumbo. But, at the end of the day, fat people eat too much. Period. Mass is not created out of thin air. (Unless you're a plant.)
Whether this fact is "helpful" to people trying to lose weight, I'll leave to the psychologists. But, it's true. And, there are some fat people that do change their behavior when presented with the truth; namely, quit eating foods with so many carbs, starches, and sugars.
Of course they eat too much. The question is why? Taubes has a good example. If I asked you why that restaurant was so full, and you responded "because more people entered than exited," I would think you were an asshole. But CICO is the same kind of platitude. It doesn't actually tell you anything. Taubes and many others assert that the kind of food you put in your body dictates your drive to put more food in your body. Eat sugary foods, and you'll drive insulin, pack glucose away in adipose tissue, move less, and want to eat more. Sugar drives energy into adipose tissue AND slows your BMR AND drives hunger. That's a far more useful observation than CICO.
I’m always hungry. There is hardly ever a time that I feel completely satiated. In other words, there is never a time that I don’t have a drive to eat too much. It takes constant discipline to keep my calorie balance in check. As humans, we all have the mental capacity to not give in to our lizard brain.
I think the fundamental mistake of the last three decades of health advice is overestimating that capacity in the face of declining insulin sensitivity due to persistently high glycemic loads.
Well... sort of. There's a major difference in that restaurants usually don't have the ability to directly control how many people enter and how many people leave. So pointing out that there's an in/out inbalance is useless, as you say, since there's nothing that can be easily done about it, and that's obvious, so the person asking the question probably didn't want to know that.
In the case of eating, you can control directly how many calories are coming in, and you have at least a little control over how many calories are going out. So in fact CICO is very often useful: it's a kind of promise that if you cut your intake sufficiently you will lose weight.
It's true that certain diets will make you want to eat more calories: but the promise of CICO is that if you ignore what you are inclined to do, and simply focus on your intake, you will lose weight.
Obviously you are better off adjusting your diet too, but that's because doing so makes it easier by burning slightly more calories and making you slightly less hungry. What you're doing is a sort of sociological analysis: figuring out why people eat too much. Sure, if you can come up with tricks to eat less that help dieters, that's great, but people who want to diet fundamentally have to learn to ignore the instinct to eat and limit their intake.
Your body of course doesn't use energy it doesn't have. But it can balance the equation by restricting the output - lowering muscle repair (so post-workout recovery is slower), lowering brain supply (lowering concentration), lowering heating (so you fell cold), etc.
Whether the body decides to use stored energy or lowers output (while signalling hunger) is mostly hormonally controlled, by insulin and glucagon - this is why insulin resistance is such a problem.
Some research seems to show that portion restriction leads to lowered output while increasing time between meals (i.e. not snacking) lead to use of reserves, but I don't have a nice article to link.
Your bodies absorbsion of nutrients and yes calories is not a system in a vacuum. Nor it’s decision to store excess calories as fat. There’s a wide range of how much different types of foods affect different people. I had a friend who would eat (we counted) 4000 calories a day and couldn’t get over 120lb. Turns out they had a soy allergy and their bodies didn’t absorb the food.
Simplifying it to calories in calories out is a generalism of a generalism.
So your friend was unable to digest at least a thousand calories a day, likely more, and didn’t see fit to mention the endless diarrhea they must have been experiencing? If you’re spewing a thousand undigested calories out of your ass every day, you should know something isn’t right.
Yes, nobody is disagreeing with physics. But a discussion about weight gain/loss that always has people saying "calories in = calories out" is like a discussion of every business saying "well profit = revenue - expenses". Obvious but not helpful. The interesting thing is discussing how to modify those variables.
The flipside of this is that people generally want to argue endlessly about what are essentially micro optimizations instead of addressing the core issue. Maybe your gut flora are “out of balance”. Maybe your metabolism is a little lower than average. Sure, there are factors that can matter. But if you’re not losing weight you’re not in a caloric deficit. If you’re not gaining weight, you’re not in a caloric surplus (or you’re spewing diarrhea and should talk to a doctor).
Address the core issue first before arguing about minutiae. The emphasis on relatively low impact factors is especially unhelpful and unhealthy because people latch onto all these discussions as justification for why they can’t lose weight. Sure, an obese person might have a low metabolism[1], but if they eat 3500 daily calories and live an entirely sedentary lifestyle, those are probably the major causes.
[1] But they don’t. Study after study have shown that obese individuals have high metabolism because metabolism is tightly correlated with total body mass.
Most people aren't fat because they're lazy. Most people are fat because they eat too much. We have a culture that glorifies food, junkfood more than the rest. Overeating when eating junkfood is absurdly easy. Teaching people how to eat healthier and eat less is the best known way to help people lose weight.
Constantly talking about genetic predispositions, obscure metabolism suppressing viruses or gut flora does about jack shit to help people lose weight.
The minor difference between the weekly calorie expenditure of the average person and the morbidly obese is mostly meaningless. It’s much more about how much they eat.
That’s because waste generally doesn’t contain any significant usable calories. If you’re passing undigested food then obviously it starts to matter, as abusers of laxatives know. It’s not typically discussed because it’s not typically a meaningful factor and if it is you should already know.
Yeah, crapping out calories is a time-honored tradition among people with eating disorders who don't like to vomit.
Your body doesn't care how the calories go out. If they're gone, they're gone. If you eat 3000, but crap out 2000, your body doesn't say "Yeah, well, that's not how you usually get rid of calories, so get fat."
Just because our methods of recording aren't perfect doesn't mean that the core idea is wrong.
The point is that the body adapts to burn more or fewer calories depending on how much you eat. Restricting calories can possibly have the side effect of just lowering your metabolism, rather than just losing weight.
Restricting your calories and causing lower metabolism only works for so long. Otherwise a person would not be able to starve to death, which is obviously not the case.
Why are you bringing extreme cases when they're not relevant?
Reduced metabolism when dieting is a thing, and it's also correlated to weight loss. Less weight, less base metabolic rate. Down to a point which is irrelevant.
It gets tricky because calculating calorie consumption is really hard (how much of what you ate was actually turned into energy) and calculating calorie expenditure is probably even harder.