I have a related question: Can the calorie count reliably predict the effect on a persons weight? Or is the amount of carbohydrates and fats much more important?
The body isn't perfect, and will never absorb 100%. You can figure how much by measuring calories left in feces (it's very little, our digestive system does a great job).
This waste will vary slightly. Heavy processed food and sugars will be close to 100% absorption, harder to digest food can be slightly lower, but still within ~10%.
The reason we recommend lowering high fat, high carbs and sugary food to people isn't because calories are different, but because it is a lot easier to consume a huge amount of calories through those.
Think about 500 calories.. That's 1l of soda, or 2 candy bars, or one Big Mac. All of those are very easy to eat/drink mindlessly. Now compare eating 1.2kg of carrot, 2.5l of vegetable soup or 500g of rice.
We might never have full pictures of all these questions.
[1] http://examine.com/faq/what-should-i-eat-for-weight-loss/
[2] I know specifically that this is currently being tested in some large-scale, high-cost studies. Which tells me that researchers aren't as confident as [1] makes it sound like.
As for your last question (food composition and satiety), tangentially related, in the literature regarding this it seems as if keto has a lot of support for weight loss. Not because of the way it affects your metabolism or gut bacteria, but because it does satiate people more adequately than other diets it was tested against (regular western, Scandinavian and paleo).
Keywords if you want to look it up more: TDEE, 1 pound = 3500 calories, calorie in calorie out
Your metabolism level, and the percentage of calories that are actually taken up by fat cells, depend on many factors besides total calorie count.
A nice paper that came out recently: https://www.sciencedaily.com/releases/2015/11/151119143445.h...
So, for example, person A can eat 3000 calories of cookies per day, but would gain weight on 3000 calories of rice. Person B could be the opposite. From the paper, it looks like genetics is a factor, though epigenetic factors and microbiome seem more important.
That's not at all what that paper says. It describes that blood glucose response to various foods can differ between people (and shows to extreme outliers as examples). Your interpretation with "3000 calories of cookies" vs rice is both not supported by the study, and also nonsense.
I'd look up the studies for this if I had the time, but: the actual correlation (relationship) between calories and weight gain/loss is extremely large, with the differences between most people of similar body types less than 200 calories/day.
Yes, it is well supported by the research, did you actually read it?
I actually had a nice phone call with the lab that produced this paper. You can explain a percentage of weight changes by calorie intake, but the factors that explain glucose curves (and thus uptake of calories) require far more data (like genetics, etc).
I read your link. It's about blood glucose. Not about weight. The crux of your argument is that blood glucose response equals uptake of calories, which is not supported by your link, and which is not true. If it were, you could eat 5000 calories of fat in a day, have no blood glucose response, thus not get fat.
Are you really trying to claim that the outlier participants of whom the blood glucose plots are shown in your link are unable to use any of the calories in bananas/cookies, because they had no blood glucose response?
Regardless, we can talk about metabolic pathways. If you consume carbohydrates, they eventually get dumped into your bloodstream as glucose (minus fructose, which is special). The level of glucose then absorbed into fat cells is regulated by insulin, and insulin production (while more complicated) is determined by the level of glucose in the blood.
I don't see what fat cells have anything to do with this either.
As for your rebuttal of my points, it does not seem sequent. I made the point that two individuals eating the same food will gain weight differently. You then made the very same point by linking to another paper which by the way does not support what either of us said - as it measured individuals individual glycemic responses to different foods, which is not correlated with the body's calorie intake on the food.
Here's the full paper in case you did not read it (and for others to read if they'd like): http://www.sciencedirect.com.sci-hub.cc/science/article/pii/...
As for the paper, the graphics used represent outliers. Plus they in one example compared cookies and bananas. Both which have different metabolic pathways. Fructose is handled in the liver and glucose is not. When they compared bread and glucose the difference was not quite as drastic even when comparing outliers. Therefore it seems more like it has to do with varying ability in people's bodies efficiency to metabolise fructose and glucose.
Everything in between is affected by cumulative margin of error. There are inaccuracies when calories are calculated, then variations of portions, variations of individual metabolism and compositions of gut bacteria. If you throw the "not all calories are equal" in the mix you get even more variations.
Noteworthy however is that with change to body composition, your TDEE (known as the amount of calories your body needs to maintain its current weight) changes. However it can easily be accounted for when losing (or gaining as may be the desired outcome for some people) in a controlled way.
Regarding the different metabolism thing: https://examine.com/faq/does-metabolism-vary-between-two-peo... (To asnwer the link's question: Yes. 600 at most calories if you compare two outliers.
You can kick a heroine habit by quitting. You can never stop eating. How successful do you imagine most junkies would be if the standard advice was "measure the amount of heroine you take per day and stay below your target".
Yes. There was a MIT (or something) prof that went on a mission to prove this. Ate crap junk food...but counted the calories...and lost weight.