rachelmanija | Debunking food, fat, and fitness myths

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Debunking food, fat, and fitness myths

I would like your best recs for in-depth articles, studies, or books on the most cutting-edge current knowledge about nutrition, body weight, and health.

I am NOT interested in basic articles about very well-known ideas like fat will kill you, carbs will kill you, meat will kill you, anything your grandma wouldn't recognize as food such as everything but cabbage and turnips will kill you, etc.

I am also NOT interested in articles with a primarily political bent (i.e., "pushing diets on women is based on sexism/capitalism not science;") I agree with that, but I'm looking for stuff where the meat is science and the politics is the side dish rather than the reverse.

I'm looking for more in-depth, up-to-date information on topics including but not limited to...

- Do we actually know anything about nutrition, given the every-five-year swings between "eggs are cardioprotective/eggs are a heart attack on a plate," "fat is the Devil/carbs are the Devil," etc? If so, what is it and how do we know it?

- What is the actual science on grains (and no, I don't mean Wheat Belly)?

- What is the best and most cutting-edge knowledge on gaining strength?

- What is the actual science on the causes of Type 2 diabetes, why its prevalence has risen so much, and its association with obesity?

- What is the actual knowledge of the diet and health of "cavemen?"

- What is the actual science on being fat, thin, and in-between in terms of health? For instance, is it better to be fat and active than "normal weight" and sedentary? (I know the answer but I'm looking for something that goes into this in-depth.)

- What is the deal with "calorie reduction makes you healthier and live longer" vs. "dieting is bad for you?"

I'm already familiar with Michael Pollan, Barbara Ehrenreich, Mark's Daily Apple, Diet Cults, Body of Truth, and The Starvation Experiment. And lots more but those are the things I get recced a lot already.

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I work on energy balance, metabolism, and leptin, albeit at a jaunty angle from people studying human body weight. Let me see what I can tease out for you. In the meantime, books you might find interesting that you haven't listed are Marlene Zuk's Paleofantasy and Traci Mann's Secrets From the Eating Lab. Mann's book in particular links to one of the most startling findings I've run into in years, which is that the perception of how good a food will taste/how "healthy" it is actually influences how much ghrelin is secreted in response (ghrelin being a hormone associated with being full-not-hungry, much like my leptin).

- What is the actual knowledge of the diet and health of "cavemen?"
If humans can fit it in their mouth and it won't immediately kill them, historically humans have tended to give eating it their best shot.

- Do we actually know anything about nutrition, given the every-five-year swings between "eggs are cardioprotective/eggs are a heart attack on a plate," "fat is the Devil/carbs are the Devil," etc? If so, what is it and how do we know it?
In my personal estimation, having gone digging through a bunch of this literature? We know approximately how much you probably need to keep someone alive, and we know how dietary deficiencies like rickets work. We have a rough idea of the types of diets associated with longevity, but we don't have a good idea of how transferrable those diets are to other people, and we don't really understand well how adiposity (fatness) and diet fit together, nor do we have a great understanding of how these things interact with other things (like STRESS). We know that if you feed mice and rats very high-fat diets, they will become obese, and we know that it's very hard to get people to sustainably change weights outside of about 20lbs away from their "set point". We do not understand how "set points" get set or why they change over time.

- What is the actual science on being fat, thin, and in-between in terms of health? For instance, is it better to be fat and active than "normal weight" and sedentary? (I know the answer but I'm looking for something that goes into this in-depth.)

It's better to be active. If you want it, I'll go digging for the primary literature, but the Mann book also talks a lot more about this in a lot of detail, and I would probably start by looking into her citations.

Oh, and before I forget--let me just point out that stress, especially chronic stress, is a huge factor in weight gain, to the point that one of the existing models for obesity in rats is stress-induced hyperphagia. I cannot overestimate how much energy balance and stress are hooked together (as are things like reproductive investment and social context). I would be very interested in looking at overall stress levels in the context of modern weight gain, personally.

In the meantime, I'm looking at the interactions between cortisol and leptin in the context of social behavior, and I'm really excited to see that data once I can successfully analyze it.

That doesn't explain why I've never been able to gain weight!

(Just kidding, I know it's genetics and having to walk everywhere.)

I left this tab open to see people's replies, which I'm finding very helpful--including this one. *fistbumps*, perhaps? I can't keep weight on despite trying to gain 2 kg at times, and currently I have both immediate stress and the processing of long-term (cPTSD) stress. *shrugs* I too walk a lot, FWIW.

*fistbumps* I just want to donate blood!

I hear you.

Thank you very much! I haven't read either of those.

I'd love to hear anything more you come back with!

Incidentally, my context for this is being incessantly bombarded with demands to adopt some diet. Most recent was two successive doctors telling me to become a vegan, and telling me to go ultra-low-carb to the point of not eating apples or oranges, and only eating small amounts of berries spaced out throughout the day.

I'm not overweight IMO or according to the BMI, but after 1) losing a third of my bodyweight due to illness, then regaining it, 2) being over 40, 3) menopause, 4) five years of extreme, unrelenting stress, I do have high blood pressure and a fair amount of abdominal fat of the sort you can grab in handfuls. I also exercise a lot and eat a diet of the sort people like Michael Pollan and Mark Bittman and other whole-food enthusiasts would approve of, and I'm losing my mind with all the demands to give up gluten, egg yolks, meat, fruit, dairy, nightshades, foods cooked in microwaves, etc.

....yeah, pretty much no diets are evidence-based, and the paleo people in particular are, er. Well. Er.

Look, I'm not an anthropologist, but I am an evolutionary biologist, and I can tell you that for one thing we know that humans have adapted, including adaptations geared towards digestion, since the advent of agriculture: lactose tolerance is particularly well known, but we also have evolutionary evidence of adaptation to high-starch/grain diets (and not just in us--in dogs, too!). See here this interesting piece about human evolution as a dialogue between the genetics of any given human population and the culture of that human population.

Now consider variation in the makeups of human cuisines across various cultures and socioeconomic strata: everything from almost purely carnivorous to purely vegan, incorporating meat, eggs, insects, fruit, plant pith, sap, leaves, milk, flowers, seeds, grains, tubers, weird shit like honey--if it is digestible, some human culture somewhere has worked out when and how to effectively eat it. The paleo people always have some extremely specific idea of what Early Man ate and figure that humans have just been in stasis this whole time, I guess, without adapting to their circumstances. But adapting to circumstances is what humans do.

Re: diets for weight loss, you might find this paper on the long-term efficacy of diets to be interesting; it should be freely available. The short answer is that in the long term, diets don't work, and if anything the stress can increase your set point of weight. Generally, if you can't get access to a peer reviewed article you want on your own, let me know and I'll host a downloadable version.

if it is digestible, some human culture somewhere has worked out when and how to effectively eat it

My go-to example for this is hákarl: some Icelander was desperate enough to figure out that if you ferment a dead Greenland shark (whose flesh has neurotoxins) by burying it in sand for several weeks then cure it by hanging for several months, it becomes technically edible. Nauseating to people who haven't developed a taste for it, but it will no longer kill you.

(The only thing I've tried that tasted worse than hákarl was a "broccoli casserole" flavored soda.)

Like I'm not surprised they'd go that far, I just always wonder - just out of curiousity about the process - what it was that inspired them to try that.

Like it's not even unbelievable, I'm just curious what it WAS. Was there some lesser version of this where burying food made it less poison-y that they already knew? did he come along and find that some bear had dug out a shark that had accidentally been buried and cured and instead of the usual Dead Bear this bear seemed fine so like let's give it a shot? did they have to go through multiple rounds of testing? XD XD

There was! Gravlax is literally "buried salmon," and was originally made by burying the fish in sand to ferment. So, yeah, someone decided to apply the salmon-curing process to the poison shark and see what happened.

Edited 2019-04-25 02:39 (UTC)

WILD RIDE FROM START TO FINISH

The closest one to having any "evidence based" is the whole "Mediterranean diet" one which, as far as I can tell, you (Rachel) more or less already follow.

http://thischangedmypractice.com/weight-loss-in-healthy-people/ this is the post (the basic site is maintained by UBC med school) that made my mom hush in her previously slightly-annoying-standard-for-mainstream fixation on what I ate, and it has a crapload of sources at the bottom.

I mean it seems very very clear to me that what's happening is you're running into people who don't realize that this shit is not "do this and you Will Be Healthy", it's "do this and the shit that we know gets caused by not doing this won't happen, or won't happen as much, but actually there's so much other shit that could happen that who knows whether you'll actually be healthy or not, it's just you won't be for sure LESS healthy?"

It's like, if you're miserable-angry AND you haven't eaten or slept well lately, the first good step is to eat and maybe get some solid sleep, because those things are enough in and of themselves to cause Misery and Anger, and that way you can eliminate them as potential causes.

BUT you might still be miserable and angry later, because they're not the ONLY things that can cause them. So.

tl;dr as far as I can tell you are in fact doing everything "right" and you're just getting shitty luck, and also shitty luck in running into doctors who find this offends their just-world fallacy comfort zone.

I'd like to say that I generally agree with your summary, with one addition: it's not merely about human evolutionary adaptation to diet, but the human microbiome—our gut population do a lot of pre-digestion.

In particular I note the use of antibiotics in animal feedstocks going back to the 1940s because they make animals put on weight, and that the obesity epidemic in humans post-dates the introduction of antibiotics (and spread around the world to some extent regardless of variations in local diet). I'd love to learn of a cross-cultural study of obesity rates against antibiotic prescribing in the under-5s: I suspect there may be a connection. And this is before we get into the existence of things like SMAM-1, Ad-36 and other obesity-inducing viruses.

Upshot: it's really complicated and we aren't close to understanding the relationship between food inputs and metabolism in anything but the crudest way—by implication the immune system, inflammatory response, our commensal gut bacteria, and possibly zoonotic infections are all involved to some (maybe little, maybe a lot) extent, and focusing purely on diet is to risk missing the point.

Edited 2019-04-25 12:33 (UTC)

If there's not one yet, I expect there will be one (or more) in upcoming years, as I just dropped "obesity antibiotics" into the search at the library where I work and it's popped out a lot of articles and small-sale studies about the correlation of early childhood antibiotic use and obesity, starting in about 2012, and getting more frequent in 2015-2018.

If humans can fit it in their mouth and it won't immediately kill them, historically humans have tended to give eating it their best shot.

And if it does immediately kill them, then the person next to them has said "Huh, whoops - but what if we leech/ferment/bake it first?"

Eventually one gets hungry enough that it's either TRY eating it and MAYBE die, or don't eat anything and die FOR SURE, and at least a few people will do the former. XD

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