What's so hard to understand about that..? Maybe I am missing the point. Is this just to gather more evidence to prove caloric deficits are the correct way?
However, the "calories out" portion of that equation is actually quite complicated. In recent years many studies have indicated that the body does not process all calories in the same way. So "calories out" depends on a lot of things, including:
- metabolism, which can be increased by exercise and muscle mass
- what specific kind of "calories in" you're getting, and how your body processes these
- calories burned directly by exercise
To highlight one specific example of this, a calorie of fructose may be processed by the body very differently than a calorie of, say, vegetable fat: https://www.youtube.com/watch?v=dBnniua6-oM
The "calories in" part is more complicated than people like to admit too, and probably more important for weight loss. The way our body handles hunger and its relative primacy in our mental state makes it unnecessarily difficult to calorie restrict and then maintain, when eating certain diets. It's like telling an alcoholic "just stop drinking, duh" or an insomniac "just relax and sleep, simple as that". Just because something is in our brain doesn't mean we have full control over it, and I'm not sure why food is treated like something that everyone magically has complete self-control over, in contrast to _literally everything else_.
I'm really really fortunate to have grown up in a good food culture, and worked on it a little more in college. Meeting CICO goals and losing weight when I want to is really not that difficult for me, but I don't think this has much to do with self-control or my genetics. The way I eat just makes hunger less of a factor in my life: I rarely get hungry, skipping meals is never a problem, I get satiated quickly, etc etc.
I think of this as the "calories in" portion. There was never any reason to assume the means by which we measure the caloric content of food truly represented the caloric energy available to the body.
I'm not sure what chemically needs to happen, fat is transported from the bowel to the bloodstream in a relatively complex process, but once it's in the blood, it's in the same form as in storage, as triglycerides.
In fact, the triglyceride content of a person's fat stores will reflect their diet, which is a strong indication it comes directly from the food without processing: https://www.ncbi.nlm.nih.gov/pubmed/4072956
That's not at all true.
CICO is a straightforward restatement of a law of thermodynamics, and I'm not disputing that at all.
But from a weight-loss perspective, understanding CICO isn't necessarily that helpful, and certainly not "the key". The difficult question is how any particular individual can make CO > CI. (Well, actually, the goal is to balance CO with CI at a healthy weight, but of course that's step 2 for a lot of people.)
There are many millions of people for whom the answer to that question is not known.
I suspect it's because Human metabolism is complicated, with numerous overlapping and interacting mechanisms and system, where the parameters for how they interact vary by individual... hormones, habits, social network, culture, taste, access to food options, physical health, your job, etc., can all be significant factors, depending on the individual. Meanwhile, food producers of various sorts are often acting at cross-purposes, since their goal is to make as much money as possible, not necessarily help people lose weight.
The Second Law of Thermodynamics applies to closed systems only. Show me the ecosystem where food consumed and a human body is a perfectly closed system with no other inputs/outputs and I'll show you how that does not resemble the real world and you are making underlying assumptions you cannot prove.
The real criticism, however is that you cannot just assume that CICO is a restatement of the Law of Conservation of Mass-Energy, because it relies on the spurious assumption that "nutritional calories" are sufficient approximations for the entirety of energy in the system.
There's been a ton of work in chemistry and physics to untangle the mistakes of phlogiston theory, and caloric theory [1]. The SI unit of energy is now the Joule to absolutely distance from the problematic "calorie", and the confusion between what nutrition studies call a calorie and what Physics calls a calorie and what Joules are is an amazing mess.
Nutrition "science" seems to me like the last bastion of some middle ground between phlogiston and caloric theory, and CICO the battle cry of its devout believers.
The average american eats 3600 calories per day. Fat ones eat more; perhaps 4000 to 8000. This is far beyond amounts recommended to lose weight effectively: 1500 or less.
There are lots of variables in human nutrition and metabolism, but the biggest by far is the fact that people are eating 3-5x the amount of food they should.
If you think obesity is due to the difference between 80 calories or so, you have other drastic immediate concerns (the terrible mental model being one). People aren't becoming obese because their body isn't "processing" fat calories compared to carb calories, they are obese because people eat obscene amounts of food daily.
Countries like France and Italy eat massive amounts of carbs in their diets and they don't have obesity issues on the scale of the United States.
CICO is empirically vacuous.
The biggest factor is nutrition.
Yes!
> The point of these is body positivity basically. You are fat and it isn't your fault.
I didn't see this at all in there. If anything, this is written to people who think they can outwork a bad diet, which is rarely the case for anyone over 16. Nothing in there was about body positivity or anything. It just showed that even when we run and "burn 300 calories" that you are possibly holding that back somewhere else to stay at caloric balance.