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Comment by codeableconcept | Hacker News Reader

This is similar in terms of macros to the traditional Irish diet in the 19th century, which for workers was purportedly made up of around 13 pounds of potatoes a day for an adult man. This traditional Korean diet appears to also be extremely high in carbs as a proportion. Of course these groups had significantly higher energy expenditures than most moderns, but it does seem possible that caloric excess in the absence of significant dietary fat does not drive obsesity / metabolic disease in the same way.

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What's the hypothesis there? Were they just shitting out the extra starch without digesting it? Due to conservation of energy the calories can't just vanish.

It doesn't seem physically possible for most adult men to consume 13 pounds of potatoes a day. I'm a large man and I think I'd burst or vomit before choking down that much, regardless of how hard I'd been working. Most likely that number is just wrong.

Hypothesis is that the irishmen were doing hard physical labor that required a high caloric intake. PCT thru-hikers consume 4,000-4,500 calories per day (at least I did) while staying thin. According to inter-net, 13 lb of potatoes has about 4,500 calories. Apparently US civil war soldiers expended 3-4k per day.

I was responding to the claim by @codeableconcept that the absence of significant dietary fat somehow prevents obesity, independent of energy balance. That seems unlikely.

Obviously it's possible for an active man to expend ~4500 kcal/day. I've done it myself many times. Even back during the Civil War, US soldiers typically consumed more energy dense food and only got a fraction of their calories from potatoes.

>it doesn't seem physically possible for most adult men to consume 13 pounds of potatoes a day. I'm a large man and I think I'd burst or vomit before choking down that much,

Presumably you aren't doing hard manual labor every day.

Not every day now, but I've done enough hard manual labor to know that it wouldn't allow me to eat 13 pounds of potatoes. Seriously no one was eating that much on as regular basis.

>Not every day

There's the difference.

Once you spend every single day doing hard manual labor for years consuming potatoes for the majority of your calories then tell me 13 pounds is impossible.

Sure, its impossible for you now, but that's totally irrelevant. An equivalent statement would be "it's totally impossible for a human to throw a baseball at 90mph, I tried for a whole week once and I only threw 40mph."

If your diet is 90% potatoes and you do hard manual labor all day, you would absolutely need about 7 pounds of potatoes (2500 calories). I don’t think 13 pounds seems that crazy. I have sat down at a meal and eaten 3 pounds of potatoes before.

A little off topic, but there is this joke:

A Russian and American soldier meet during some peacekeeping mission/veteran fair and discuss which army is better.

They go through weapons, the American really likes AK-47. They talk about training. They discuss the distributed vs centralized command.

Finally the American says that they eat 5k calories per day. The Russian suddenly jumps up, points his finger at the American and starts yelling: "Liar! Nobody can eat that much potatoes!"

13 pounds of potatoes is about 4600 kcals. That's in the range of what an NFL athlete consumes in a day.

The problem is digesting that quantity of food, not the energy content. Elite athletes typically eat some potatoes but most of what they eat is more nutrient dense.

Seriously guys, get out your scale and weigh 13 pounds of potatoes. Could you really consume that much volume in a day without feeling sick? Let's do a reality check here.

About 6 weeks into a cross country bike tour, I spent a rest day eating all day. I think I ate 4 massive burgers and a large supreme pizza. Probably somewhere around 6000 calories.

A week prior, I ran out of food in the mountains. I finally got to a store, bought a loaf of bread, a pack of Oscar-Meyer bologna, a pack of cheese slices, two sodas, and a red bull. When I left the bench near the store, I had a few slices of bread left.

When you put out incredible amounts of energy, you can eat a fairly incredible amount of food. I don't understand where the food goes, it really doesn't feel like you should be able to eat that much volume but you can.

Those foods you ate are all more calorically dense than plain potatoes so my point still stands. It's not about the calories but the total volume of food that the human gut can process in a day. Have you seen 13 pounds of potatoes?

Potatoes are ~0.7kg/L, so that's ~8.4L of potato over the course of the day & 370 grams per waking hour, which is one big potato.

Yes my examples were somewhat high energy density but in the second example, I probably had 3L+ in my belly in just one meal. Honestly I think your body just gets used to it.

I'm not familiar with the 13 lb of potato claim, but it strikes me as a stretch (hah!) but not inherently implausible.

I had a HS friend who was a serious swimmer (not quite Olympic level but he won state championships) and watching him eat was insane. He would eat about 3x of what we all ate. Like literally down 3 sandwiches while we had one. I think he was on a 6000 calorie a day diet. I believe the potato thing. It sure sits outside what I think I could eat, but having seen others do similar, it seems realistic.

I do weightlifting and have gone through times where I do more weightlifting and less. The body just absorbs food when you do more work. Can't tell you the mechanics but it's way easier for me to digest more food when I do more weightlifting.

I thought human bodies adapt to strenuous effort and become more efficient over time. Meaning your average keyboard jockey might need 4000 calories per day if they become a manual laborer. But over time their body would adjust and they'd be able to get by on maybe 3000 calories.

Human bodies don't adapt much to become more metabolically efficient. Some endurance athletes will gain a few percent after extensive training but the effect is small.

For some activities there is a skill and technique aspect which impacts the amount of energy required. Like if a keyboard jockey literally doesn't know how to swing a pickaxe effectively then they're going to burn more calories digging a ditch compared to someone who's been doing it for years.

> Human bodies don't adapt much to become more metabolically efficient

https://www.scientificamerican.com/article/the-exercise-para...

That's not what recent research indicates. The author has written a book about this as well.

It's the key evidence behind the idea that you can't outrun your fork. To lose weight diet is the only way. Exercise gives you a nicer-looking, stronger body but it can't do much to make you shed fat.

That's a weird thing to be downvoted over. I didn't realize I was saying anything controversial.

The Irish had milk also with all the potatoes. It made it a diet that could keep you alive and even thrive.

>Potatoes and milk, particularly buttermilk, were a nutritionally complete diet for many Irish peasants before the famine, allowing them to be healthier than some European counterparts who ate a bread-based diet.

Potatoes contain all proteins, if i'm not mistaken, only less than protein rich plant sources. Wheat and rice need to be combined with other sources to get all proteins.

Potato protein quality is fairly good relative to most plant sources but still deficient in certain essential amino acids, mainly cysteine and methionine.

> it does seem possible that caloric excess in the absence of significant dietary fat does not drive obsesity / metabolic disease in the same way.

FWIW this is exactly the opposite hypothesis to that of the Keto diet (whereby consuming fat in absence of carbs does not drive obesity / metabolic disease)

To me seems more likely they were just burning more calories

I think you’re probably right. It is an interesting thing to think about though — since carbohydrate to fat conversion is extremely inefficient, I think you could at least expect a more forgiving change in body composition during a period of over feeding.

More speculatively, there could also be a genetic component

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