I love reading these discussions and find it positive that the world is changing. I have long had both a personal and professional interest in the areas under discussion and feel like I am pretty well informed but have to acknowledge that there are so many moving parts in each human body and its associated microbiome that it's hard to make sweeping statements.
I find much wisdom in the messages of Yudkin, Taubes, Lustig, Ludwig, Teicholz, Fung and others. The messages in my mind boil down to a few simple components: too much sugar (sucrose, highly processed starch, HFCS), too much fructose (Sucrose, fructose, HFCS), too frequent dosing with these substances (preventing insulin levels from falling to allow fat/triglyceride mobilization/utilization and likely leading to leptin resistance), too many calories in easy to access and non-satiating forms (simple sugars and carbs), too many processed foods with minimal fiber that negatively impacts the microbiome.
All of these things combine in varying degrees to lead to fat gain (most harmfully in the liver and viscera) which leads to insulin resistance and metabolic syndrome. Subsequently, the individual makes matters worse by recognizing that they have become overweight and start to 'diet' in the traditional way that makes the body turn down its metabolic rate in an attempt to prolong life the face of calorie restriction. The 'diet' ends but the metabolic rate (which accounts for the vast majority of energy burned in all but people like elite athletes) does not return to normal while caloric intake goes back to normal or increases and is still composed of foods that are bad for you.
At some point, something must give and people must realize that once people become metabolically unhealthy the road back is very difficult in our current environment. I am very fortunate to have never been overweight and never had to do much about it but at the same time I haven't had sugar in a beverage (other than milk - lactose [glucose-galactose]) in roughly 35 years and try to advocate and eat a JERF diet. I have also been a breakfast skipper (and sometimes lunch) for most of my adult life.
CICO is for sure a thing it's just that we have very limited tools to measure either CI or CO. I can eat a ton of cellulose (I enjoy celery) and that is a great deal of calories but none of them are available to me initially. Depending on my microbiome I may get some small amount of energy from bacterial break down of the cellulose and gut absorption but it isn't going to be much. As others have pointed out I can also eat exactly the same number of calories in many different simple/complex carb + fat + protein combinations and they will have wildly different effects on my glucose, hormones (insulin, leptin, grehlin, CCK, etc), BMR, satiety, etc. CO is even more difficult as BMR can differ dramatically even in the same individual and as pointed out already calorie expenditure for any given amount of activity varies quite a bit. And then we also have the huge potential impacts of the microbiome on energy expenditure.
One of the great statements above was that we don't eat calories, we eat food (or what we have been told is food). Something that has been clear to me since the 80s is that a 'calorie is a calorie' is definitely wrong. Even when we are talking about substances that can be used by human metabolic pathways. The most obvious illustration is the glucose/fructose paradox. Exactly the same chemical formula and energy content but handled completely differently inside the body. One is the primary stimulus for insulin release, the other causes no insulin release. One can be used by every cell in the body and the other is metabolized exclusively by the liver. The story of fructose is evolving but Dr. Lustig and his colleague's work at UCSF and that of others is incredibly frightening. Non-alcoholic fatty liver, which is inducible with fructose feeding and reversible with fructose restriction, was barely ever seen 40 years ago and now is an incredibly costly epidemic.
Anyway just a few thoughts. Thanks for sharing all of your thoughts and experiences.
PS As an inadvertent IF adherent for 40 years I would point out that the usual goal of IF (the 18:6 variety) is not ketosis but simply to allow insulin levels to fall low enough to allow fat cells to breakdown stored triglycerides (fat) and release glycerol and free fatty acids (FFAs). This was the normal state of affairs until we went on the 'snack, fuel you body, don't let your glucose get low' craze. Glycerol can be converted in the liver to glucose and FFAs are the bodies dominant energy source in the fasting state. If the fast lasts long enough and insulin drops low enough (and counter-regulatory hormones which act to increase glucose production [glucagon, cortisol, epinephrine] increase) then the liver starts turning the FFAs into ketones which the brain can use for fuel (as the brain cannot use FFAs for fuel). The same counter-regulatory hormones increase glucose production from glycerol and some amino acids by the liver (gluconeogenesis) to provide the small amounts of glucose that are necessary for a small number of cells (e.g. RBCs) and to keep mitochondria running. Sorry too much maybe.
). The thread was about keto and other diets and what works and doesn't work to lose weight. I still maintain that:
