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?
All calories are almost equal, as long as your body is in proper condition to absorb them.
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.
I think the answer is that it's really hard to study this, since food diets are hard to control over long periods of times but that current research is consistent with calorie counts being a good estimator of a person weight gain/loss. Here's a reasonable summary with some studies you can look at for the details. [1] But this is certainly an area of ongoing research and the devil is in the details: does it matter when you eat? [2] Does your gut microbiome affect it significantly? Genetics? Is there inter-person variation in how their body adapts to different food? Does fat/carbohydrates/protein/fiber content affect satiety in a manner that helps people lose weight in real life situations even if it doesn't matter in a clinically controlled setting where overeating is impossible?
We might never have full pictures of all these questions.
[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.
I won't link to any studies but regarding [2] (gut microbiome] does affect it ever so slightly. I'm just stating things from memory now, but I remember reading that our gut bacteria now is different from 50 years ago in such a way that a person eating (for example) 2000 calories then, would now have to eat 2200. Made up numbers, but the effect was between 5-20%.
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).
Reliably? Short version is no, and it is even more complicated. Two individuals eating the same food will gain weight differently, depending on a large number of factors.
Bit different answer: Yes it is possible. While it is true that two individuals eating the same food will gain weight differently, if you count your calories and measure everything you'll eventually learn (In the body building community we usually say two weeks) how many calories you need to keep your weight. With that information, you can adjust your calorie intake to lose weight. Say your maintenance is 2500 calories, then by eating 2000 instead, you'll lose 1 pound a week.
Keywords if you want to look it up more: TDEE, 1 pound = 3500 calories, calorie in calorie out
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.
The question I responded to was along the lines of "Can calorie count reliably predict the effect on a person's weight?". Now my conclusion is that your answer that "The short answer is "no"" is wrong.
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.
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.
>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).
Your call with the lab is an attempt to appeal to authority. Also, thanks for the "sigh".
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?
Apologies, but the "sigh" was for the "not supported by the study, and also nonsense" comment. I find it annoying when supported arguments are dismissed out of hand without compelling counter evidence. It sounds childish, like "no you are wrong, because naaaah". If that wasn't what you meant, please be more thoughtful.
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.
At the extremes the effect on the weight is very predictable. Keeping everything else the same when you reduce your calorie intake to zero, you will reduce weight. Or increase your intake to 3 x recommended daily values and your weight will go up.
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.
To directly answer your question: if you want to use a heuristic for losing weight, it should not be to count just carbohydrates or just fats or both together -- but your total calorie intake.
No, because different people have different metabolism. Think of it as if the body has a "target" weight. It actively tries to reach that weight and can compensate overeating (easily, by throwing away excess food) and undereating (not as easily but still can compensate a lot). This mechanism interferes heavily with your diet and that's the reason you can't easily change your weight at will by changing your diet.
It changes over time if you permanently change your diet and lifestyle, but takes years.
The body is homoeostatic and will try to repel any change in body composition and weight. While it is also correct that different people have different metabolism and gut flora that affects our calorie conversion from different foods, the answer is yes. If you count your calories reliably, you can reliably lose weight by adjusting your calorie intake to match your body. If you throw out your body's own function of regulating its weight by measuring your food, you can accurately predict what you'll weigh in, for example, five months. It does not take years.
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.
This also requires overriding millions of years of evolution and multiple levels of body systems all screaming "you're hungry, EAT EAT EAT".
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".
