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Comment by yourkin | Hacker News Reader

I have heard this recycled notion about carbs being scarce many times, but in this context it makes little sense. If fat adaptation is so efficient at converting food to energy and there is more fat around than carbs, why would the craving for carbs evolve even? I have also done keto a couple times and my experience is the same — in a month I just can’t stand anymore meat and bacon and going back to a balanced diet feels very good. I also can‘t stuff myself with carbs and start seeking both protein rich foods and fatty. Would question the whole „carbs where scarce, so we evolved to overfeed on them“ dogma. Why would fruits be more scarce for a non predator (as where human ancestors), than meat? It feels like a whole lot is missing in the story.

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Carbs and protein are water soluble while fats are lipid soluble, and your cells preferentially burn water soluble molecules before lipid soluble. There can be tons of energy in the form of fat available, but to access it you will first burn up your available protein. This protein is necessary for things like cellular repair, muscle growth, etc. You need to sacrifice this to access your energy stored in fat - an acceptable tradeoff when you're freezing in the middle of winter, but certainly suboptimal. Carbs on the other hand will burn preferentially before proteins, so you can have your cake and eat it too. Carbs can't be stored for very long, but they can be readily converted to fats for storage.

In the past, it wasn't so much that carbs were rare as calories in general were rare, and carbs were merely the most desirable. If you're an athletic hunter gatherer, you want as many carbs as possible for fuel so you don't have to switch over to your small reserve of fat and give up your proteins along the way. On the other hand in the modern day it's easy to get more carbs than we can burn in a short period of time so we have a lot of excess calories that get added to our emergency supply. Since we actually have to go through a good bit of effort to starve in the modern world, we never switch over to our emergency supply and thus it never depletes (ie we get and stay fat).

Of course you crave carbs after eating mostly proteins and fat - as far as your caveman brain is concerned, you are starving and need real food. It's just an unfortunate reality of our modern civilization that most of us don't have the metabolism to support a caveman's diet.

> in a month I just can’t stand anymore meat and bacon and going back to a balanced diet feels very good.

90% of curries are keto friendly, Thai food that doesn't involve noodles or rice, a-ok, tons of Chinese dishes are also 100% keto!

Going on any sort of restricted diet is going to involve learning how to improve your cooking game, but after years of Keto I can put together meals for large groups of people that are 100% keto and people won't even notice, and that is including the hazelnut cookies with chocolate ganache for dessert!

> Would question the whole „carbs where scarce, so we evolved to overfeed on them“ dogma

I agree historical evidence may be lacking, but a large percent of the population[1] do overfeed on carbs and a mix of carbs+fat, in a way that is has dramatic health consequences.

The way I always like to put it is, between a stuffed baked potato, and a steak, what will people at more calories of when given a chance? I know for me it is the potatoes, I can easily go through 2 entire potatoes, stuffed with sour cream, chive, shrimp, and cheese. (and I know the shrimp sounds super weird in there, but trust me, try it, it is amazing!)

That is 800 calories, and after that I'm going to wait 15 minutes and resume the rest of my dinner for yet more calories!

But if I start with 8oz of steak and some well prepared kale, well, I'm done for the night. ~700 calories total for the entire meal, rather than starting with 800 and working my way up from there!

The thing that changed my mind was realizing that skipping the bread at dinner didn't make me any less full.

[1] Such unhealthy habits are spreading world wide!

Thai food and often involve palm sugar in what you’d consider savory dishes. And depending on the brand of coconut milk that’s used you could be nabbing extra carbs there too. So even without noodles and rice you may be sneakily pushing up against your daily carb limit and not realize it.

Odds are a Thai curry for dinner isn't going to break the bank assuming it isn't one of the super sweet Americanized places.

I have seen some places that pour on the sugar, I just don't order from those places twice!

Calorie counting is illuminating. I've been able to eat 4000 kcal of mostly carbs in one sitting and perhaps up to 7000 kcal in one day, and I need some effort to eat 2000 kcal of meat/fat in one sitting (about 1kg of steak).

In general I tend to overeat carbs and go above my daily calorie intake if I were to eat until satiety, whereas I tend to eat at or under my TDEE of meat/fat and have to sometimes force myself to reach my daily requirements.

How much of the carb overfeeding is marketing and conditioning though (and mostly a US-centric phenomenon)? Any caloric excess is bad, nothing special about carbs. Demonizing one particular nutrient seems like a silver bullet and I could also enjoy 50 different ways to make eggs and ham and 50 varieties of brie and keto bread, but something felt amiss. That said, still want to try going 100% vegan someday.

> Why would fruits be more scarce for a non predator (as where human ancestors), than meat?

Seasons change?

Meat is available year-round but can be dangerous to acquire and prepare safely.

Fruits/veggies are easy but seasonal food sources that store poorly, and with vast competition.

Grains and tubers are difficult to transport, spoil, and are of limited supply determined by the growing season (especially without agriculture).

Our hunt & gather ancestors followed the seasons far closer than farmers. At least on gut check, it seems fat adaptation would be strongly selected for as well as a strong taste for carbs as available

Also not to forget that modern fruits and vegetables are nothing like the ones we've spent much of our evolution with. I would guess honey would have been the most sugary thing available, and still guarded by a swarm of angry bees.

Was/is there that much of seasonal variety in the African regions, where humans evolved mostly? And why should we stop at humans and not go back even further?

Maybe, in essence, the bacteria that we host to help break down carbs start producing something that makes us crave/prefer carbs?

It seems like the bacteria would, in essence, be self interested and might have developed their own evolutionary mechanism to promote the supply of their food source?

In other words, if we, essentially, keep internal bacteria colonies to help break down specific types of food, those colonies may encourage consumption of their specialized food source?

We may also, symbiotically, encourage the preservation/maintenance of internal processing capability?

>Why would fruits be more scarce for a non predator (as where human ancestors), than meat?

Because there exist more competitors for the fruits. There are more plants than there are herbivores than there are carnivores.

On the contrary, there are orders of magnitude less megafauna than plankton. And there’s a diminishing range in between. It’s easier to get berries for dinner, than boar. Of course, things could be the opposite during Ice Ages, but that’s just a glimpse in geological time, not convinced that metabolism would change entirely during that period.

Guess you didn't understand my last sentence because it's not contrary to what you written.

There are more boar eating the berries than there are of you.

A trip to the woods would with a high likelihood show that there are more berries around than berry eating boars. But my point is not that there is no competition for resources, and not that there always was an abundance of everything, but that the carb scarceness theory is not a complete explanation. Because food in general was scarce, and we either should have the same cravings for other nutrients or the „carb-stuffing“ notion is a bit overused.

Might be that fat was as scarce as carbs prehistorically. Have you ever eaten wild game? They are drastically leaner than farm animals. I imagine they were even leaner back when there were more wild creatures competing for the same food supply.

It's not an accident that our palate has evolved to reward us for finding salts, fats, and sugars.

Seems appropriate to mention rabbit starvation here:

https://en.wikipedia.org/wiki/Protein_poisoning

Meat-only diets are sustainable, but remove enough fat and you'll die.

Nor fat, nor carbs are an essential nutritional component. The body can not synthesize certain amino acids, but it can convert protein to both fat and carbohydrates by means of gluconeogenesis. If anything, we should have cravings for sources of protein, not sugars. One could argue that sugars provide the burst of energy for the metabolic pathway that could be make it or break it in cases where that burst gives an advantage. This, and not the scarceness argument, which seems just thin to me, although mainstream opinion.

There was a good talk at Carnivore Con in 2019 here (https://www.youtube.com/watch?v=jH7JGM7K-Lc&list=PLluvR68gTT...) about this.

The very rough gist is that there is historical evidence of pre agrarian humans starving to death with stomachs full of lean meat. In a nomadic lifestyle where they chase down prey protein costs too much energy to digest and convert into usable energy.

Fat is an essential nutritional component. As an example, cholesterol is necessary to produce hormones such as testosterone, estrogen and cortisol. Thankfully, it's pretty much impossible to avoid if you eat meat.

Carbs are not essential. You can live on zero total grams of carbs.

Also gluconeogenesis only converts proteins to glucose, not fat, at least not directly.

Cholesterol is synthesized by the liver, in sufficient quantities: https://www.sigmaaldrich.com/technical-documents/articles/bi...

believe it or not, by your definition carbs are also essential, it’s just that the body can produce them

Protein -> carbs by gluconeogenesis

Isoleucine and phenylalanine are exclusively ketogenic and produce ketone bodies.

Leucine can be used to synthesize fatty acids in adipose tissue.

The only 2 fats that we really need are omega-3 and omega-6, but not in huge amounts, thankfully, both not from meat.

Point is, one can more readily survive without a major source of fat or carbs.

How do you explain rabbit starvation then?

A quick look at https://en.wikipedia.org/wiki/Protein_poisoning

* it‘s hypothetical

* the ill effect is diarrhea

* some people have lived off a meat only diet successfully

* personal theory is the problem is not excess protein, but lack of fiber and gut biome degradation

Any mono-diet is nutritionally a bad idea, especially taken to extremes. But — one would simply not survive at all on a monodiet of pure fat or carbs.

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