People are forced to eat more than they should primarily because of hunger pangs.

I am not sure this is true in contemporary West. I suspect that a lot of overeating happens because of social cues ("I'm at a dinner party so I should eat even though I'm not hungry") and for purely psychological reasons -- from boredom and activity displacement ("I'd like to procrastinate a bit, let me go and have a snack") to hedonics ("Sugar boosts make me feel better, yay sugar!"). None of that is actually hunger.

I have heard repeatedly the argument about "calories in, calories out" (e.g. here). Seems to me that there are a few unspoken assumptions, and I would like to ask how true they are in reality. Here are the assumptions:

a) all calories in the food you put in your mouth are digested;

b) the digested calories are either stored as fat or spent as work; there is nothing else that could happen with them;

and in some more strawmanish forms of the argument:

c) the calories are the whole story about nutrition and metabolism, and all calories are fungible.

If we assume these things to be true, it seems like a law of physics that if you count the calories in the food you put in your mouth, and subtract the amount of exercise you do, the result exactly determines whether you gain or lose fat. Taken literally, if a healthy and thin person starts eating an extra apple a day, or starts taking a somewhat shorter walk to their work, without changing anything else, they will inevitably get fat. On the other hand, any fat person can become thin if they just start eating less and/or exercising more. If you doubt this, you doubt the very laws of physics.

It's easy to see how (c) is wrong: there are other important facts about food besides calories, for example vitamins and minerals. When a person has food containing less than optimal amount of vitamins or minerals per calorie, they don't have a choice between being fat or thin, but between being fat or sick. (Or alternatively, changing the composition of their diet, not just the amount.)

Okay, some proponents of "calories in, calories out" may now say that this is obvious, and that they obviously meant the advice to apply to a healthy diet. However, what if the problem is not with the diet per se, but with a way the individual body processes the food? For example, what if the food contains enough vitamins and minerals per calorie, but the body somehow extracts those vitamins and minerals inefficiently, so it reacts even to the optimal diet as if it was junk food? Could it be that some people are forced to eat large amounts of food just to extract the right amount of vitamins and minerals, and any attempt to eat less will lead to symptoms of malnutrition?

Ignoring the (c), we get a weaker variant of "calories in, calories out", which is, approximately -- maybe you cannot always get thin by eating less calories than you spend working; but if you eat more calories than you spend working, you will inevitably get fat.

But it is possible that some of the "calories in (the mouth)" may pass through the digestive system undigested and later excreted? Could people differ in this aspect, perhaps because of their gut flora?

Also, what if some people burn the stored fat in ways we would not intuitively recognize as work? For example, what if some people simply dress less warmly, and spend more calories heating up their bodies? Are there other such non-work ways of spending calories?

In other words, I don't doubt that the "calories in, calories out" model works perfectly for a spherical cow in a vacuum, but I am curious about how much such approximation applies to the real cases.

But even for the spherical cow in a vacuum, this model predicts that any constant lifestyle, unless perfectly balanced, should either lead to unlimited weight gain (if "calories in" exceed "calories out") or unlimited weight loss (in the opposite case). While reality seems to suggest that most people, both thin and fat, keep their weight stable around some specific value. The weight itself has an impact on how much calories people spend simply moving their own bodies, but I doubt that this is sufficient to balance the whole equation.

Thanks, Ishaan. That was a lot of good directions to come at this from.

I especially found a few of them novel ways to eke out more confidence from an insulated problem:

If it's a political issue, try to find out what people who might plausibly be expertish in the area yet don't seem to be invested in debating the issue think about it.

check what known superforecasters in the field think (people who have a track record of successful predictions in that area). Superforecasters need not actually be loudly engaging with the issue, just ask.

check if people who have different types of knowledge tend to say different things (e.g. economists vs. sociologists)

I'll try to remember those for questions like this in the future.

Furthermore, notion that you raise struck me:

Most things for which it is important for you to personally understand have measurable consequences to you. Why do you need the right answer to the GMO question, what would you even do with the right answer?

I suppose I've never really considered why I wanted the right answer to a question, I suppose I ascribe a relatively high weight to "understand things" in my utility function. That said, thinking about it from the angle of "What would I do with the right answer": In this case, I would do is embrace/avoid GMO foods for my personal health and safety, vote to label/not-label/ban/regulate GMO, and argue for others to do the same.

Isn't that the ideal of a democratic system: an informed populace vigorously contesting in the marketplace of ideas?

I don't want to live forever myself, but I want people who want to live forever to live forever. Does that make me a transhumanist?

I've wondered this too. In particular, for several years, at least among people I know, people have constantly questioned the level of rationality in our community, particularly our 'instrumental rationality'. This is summed up by the question: "if you're so smart, why aren't you rich?" That is, if rationalists are so rational, why aren't they leveraging their high IQs and their supposed rationality skills to perform in the top percentages and all sorts of metrics of coveted success? Even by self-reports, such as the LW survey(s). However, I've thought of a contrapositive question: "if you're stupid, why aren't you poor?" I.e., while rationalists might not all be peak-happiness millionaires or whatever, we might also ask the question about what the rates of (socially perceived) failure are, and how they compare to other cohorts, communities, reference classes, etc.

You're the first person I've seen to pose this question. There might have been others, though.

First: check whether the issue is really important: With some exceptions (voting correctly, believing the correct afterlife and not getting sent to hell) If you aren't in a position to interact with the evidence it's probably not something you meaningfully have control over. (Most things for which it is important for you to personally understand have measurable consequences to you. Why do you need the right answer to the GMO question, what would you even do with the right answer?).

Then:

-Figure out exactly what the claims really are and try not to conflate different claims (GMOs will do what, exactly?)

-Consider the possibility that the entire premise is silly ("Is God one or trinity?" "Is she a witch?") and the "consensus" is just wrong and the debate is insane. Generate some plausible third options.

-Check if the two hypotheses seem by your perception to be of roughly equal parsimony, internal logical consistency, and compliance with known evidence, and also check the third options you generated.

-Ask the basic "so, what evidence would you need to tell the difference" questions.

-all the things you mentioned (weigh expert opinions, eliminate bad arguments, eliminate experts who use bad arguments)

-look for concrete predictable things in that area, and adjacent to that area which differ according to the two hypotheses.

-If it's a political issue, try to find out what people who might plausibly be expertish in the area yet don't seem to be invested in debating the issue think about it.

-check what known superforcasters in the field think (people who have a track record of successful predictions in that area). Superforecasters need not actually be loudly engaging with the issue, just ask.

-check if people who have different types of knowledge tend to say different things (e.g. economists vs. sociologists)

-What sorts of knowledge would you need to have to answer the question vs. what sorts of knowledge do the experts in question actually have? (You might think medical doctors are qualified to talk about the effectiveness and safety of various treatments, for example, but they aren't. You want a medical researcher for that. The only difference between a medical doctor and a witch doctor is that one was trained by a curriculum developed by medical researchers and the other wasn't.)

-check for founder effects or cultural effects biasing beliefs (Again, economists vs sociologists. Also, if theologians believe in god at higher rate than biologists it might not be because of different knowledge)

What else? I mean it's a big question, you've asked after a fairly big chunk of "rationality" there.

Yes, but that shows that Eliezer probably misremembered what the 40% referred to. In that study, "40%" refers not to how many didn't benefit, but rather to the maximal benefit on a particular measure of fitness received by any of the participants:

For example, the team found that training improved maximum oxygen consumption, a measure of a person’s ability to perform work, by 17% on average. But the most trainable volunteers gained over 40%, and the least trainable showed no improvement at all. Similar patterns were seen with cardiac output, blood pressure, heart rate and other markers of fitness.

Alternately, he might've been rounding the subsequent statistic:

Bouchard reported that the impact of training on insulin sensitivity – a marker of risk for diabetes and heart disease – also varied. It improved in 58% of the volunteers following exercise, but in 42% it showed no improvement or, in a few cases, may have got worse.

So, how many is many? What fraction of the subjects were resistant on the various metrics? Unfortunately, the NS article doesn't give exactly what we want to know, so we need to find the original scientific papers to figure it out ourselves, but the NS article doesn't give citations either, forcing us to fact-check it the hard way (a long time in Google Scholar punching in names and keywords).

Tracking down sources for this article is quite difficult. Bouchard quickly pulls up a bunch of papers all revolving around similar data from what is called the HERITAGE Family Study, which has apparently been running since 1995 (the abstract to "The HERITAGE family study: Aims, design, and measurement protocol", 1995, describes it as in-progress) and there are a lot of papers on various minutia of it. So we need to search with 'HERITAGE'.

The final paragraph about the 51/72 genes seems to be sourced from "Endurance training-induced changes in insulin sensitivity and gene expression", which was published around 2004, consistent with the NS date. The general stuff about responses to exercise is much harder to track down, but after quite a bit of browsing through Google Scholar, I think it's all summarized in "Individual differences in response to regular physical activity", Bouchard & Rankinen 2001, which sounds promising since its abstract mentions "For example, Vo2_max responses to standardized training programs have ranged from almost no gain up to 100% increase in large groups of sedentary individuals".

This review covers 4 major categories:

1. VO2_max: "The average increase reached 384 mL O 2 with an SD of 202 mL O 2"; citing:

   • BOUCHARD , C., P. A N , T. RICE , et al. Familial aggregation of VO2max response to exercise training: results from the HERITAGE Family Study. J. Appl. Physiol. 87:1003–1008, 1999.

2. heart-rate during exercise, "heart rate during submaximal exercise at 50 W" ; "A mean decrease of 11 beats·min -1 was observed among the 727 subjects with complete data. However, the SD reached 10 beats."

   • original to this review, it seems

3. blood lipids, HDL-C: "They found that when the distribution of the percent changes in HDL-C was broken down into quartiles, the first quartile actually experienced a decrease in HDL-C of 9.3%, whereas the fourth quartile registered a mean increase of 18%." Cited to:

   • LEON , A. S., T. RICE , S. MANDEL , et al. Blood lipid response to 20 weeks of supervised exercise in a large biracial population: the HERITAGE Family Study. Metabolism 49:513–520, 2000.

4. blood pressure, "systolic blood pressure during exercise in relative steady state at 50 W"; "Among these subjects, the mean decrease in SBP during cycling at 50 W was 8.2 mm Hg (SD 11.8)"

   • original to this review

So that covers 4 of the markers mentioned in the NS link. In those 4 cases, going by the graphs (the data is highly non-normal so you can't just estimate from the mean/SD), I'd guesstimate that 5-20% of each show <=0 benefit from the 20-weeks of endurance exercise.

That leaves the insulin sensitivity one, which seems to be "Effects of Exercise Training on Glucose Homeostasis: The HERITAGE Family Study", Boulé et al 2005. The graphs are hilarious, almost exactly 50-50 looking, and so correspond to the NS summary of 58%/42%.

(The papers don't seem to include any correlation matrixes, but this is definitely a problem which calls out for dimensionality reduction: presumably resistance on all 4 measurements correlates and you could extract a 'exercise resistance factor' which would be more informative than looking at things piecemeal. Since correlations between the 4 measurements are not given, it's possible that they are independent and so only ~0.2^4 or <1% of the subjects were exercise-resistant on all 4 measures, but that would surprise me: it would be strange if one's insulin improved but not VO2_max or cholesterol. I don't have any guesses on how large this 'exercise-resistant factor' might be, though.)

Not all of these are as important as one another and weight does not seem to be included judging by Bouchard's silence on individual differences w/r/t that. He does cite some interesting studies on resistance of body weight to change like two twin studies.

So going by the HERITAGE data described in that NS link, exercise resistance is a thing in maybe a fifth of the population but mostly on invisible things. 40%, however, is too high, since only 1 of the 5 measured things seemed to go that high, and the specific fractions were not mentioned, so most likely Eliezer was misremembering the other two stats as the more important stat.

In this discussion there was the hypothesis that people don't want to fight aging because of the promise of eternal life from religion. When we want to convince people it's useful to know whether that's true.

The polling data doesn't seem to suggest that hypothesis when religious Brazil in general is pro-longevity while more atheistic Russia has the lowest support for longevity. Of course that are single data points but it still suggests that religion isn't the core force that prevents people from wanting longevity.

Isn't this kind of like asking why church members are more likely to believe in God?

It quite useful to understand how people come to believe and then go to Church.

But Lesswrongers are different when it comes to the question whether curing ageing is a valuable goal. Few people on LW want to die before they are 1000. That's different for the general population. It's worthwhile to try to understand where the difference comes from.

Is belief in the supernatural (crystal healing, ghosts, "something higher", that sort of thing) actually lower?

If you take ghosts in Germany as an example 79.7% say they don't believe while only 17.7 believe they do.

I think that, absent some sort of active cultural intervention preventing it, a psychologically typical human will believe in spirits and magic. I know I would.

School curriculums are written in a way to discourage belief in ghosts and not treat it as a mainstream belief. Mainstream media does the same. We don't have figures like Oprah on German mainstream TV.

Ideas about how our matter goes on to circulate through the ecosystem, or the notion that we're all made of star-stuff and are generally one with the universe, are powerful and comforting to many.

While that might be true, I don't think that people on LW are radically different on that count.