Energy from human activity

[DenCraw]

Hi.
I am Dennis, I live in Spain.
I wonder how much power could be "sucked" from a gym.
I don't know how many watts the human body produces while training, as well, I don't know what is the expected efficiency from a well designed gym machinery.(dynamo)
How much is lost in heat, and mechanical transmission etc.

best regards.
Dennis
(No. I am not planning to do a Matrix)

[tom66]

Average dissipation of an idle human is around 150 watts.

An average healthy male can output around 250 watts.

A professional athletic cyclist can output around 800 watts ~ 1000 watts in short bursts.

But the metabolic efficiency of a human is barely 20%.  If you feed the human from beef burgers, then it is probably much worse than powering things from a diesel generator.  From plants it is probably a little better.

Quick calculation. A cyclist burns about 50 kcal per mile. A quarter pounder beef burger is 225 kcal so one burger = 4.5 miles or 7.2 km of cycling.  Roughly 36 kg of CO2e is produced or negatively offset, in the production of 1 kg of beef, so our burger costs us about 3.6 kg of CO2e.  7.2 km on 3.6 kg of CO2e is about 500gkm/CO2e.

The best petrol cars are around 1/4 of that and electric cars even better, so cycling (powered by beef burgers) is worse for the environment than driving a petrol car.  Of course, vegans have moral superiority here.

[FreddieChopin]

Average dissipation of an idle human is around 150 watts.

An average healthy male can output around 250 watts.

A professional athletic cyclist can output around 800 watts ~ 1000 watts in short bursts.

But the metabolic efficiency of a human is barely 20%.  If you feed the human from beef burgers, then it is probably much worse than powering things from a diesel generator.  From plants it is probably a little better.

Quick calculation. A cyclist burns about 50 kcal per mile. A quarter pounder beef burger is 225 kcal so one burger = 4.5 miles or 7.2 km of cycling.  Roughly 36 kg of CO2e is produced or negatively offset, in the production of 1 kg of beef, so our burger costs us about 3.6 kg of CO2e.  7.2 km on 3.6 kg of CO2e is about 500gkm/CO2e.

The best petrol cars are around 1/4 of that and electric cars even better, so cycling (powered by beef burgers) is worse for the environment than driving a petrol car.  Of course, vegans have moral superiority here.

What about oil changes, timing belts, tyres, acid in batteries? I had my MTB for 12 years already and the only thing im changing is brakes and chain every 3 years. Everything else either broke years ago or doesnt need replacing.

[SiliconWizard]

I remember we already talked about that on a topic about a startup? willing to do this kind ot thing to recharge batteries while people would be pedalling on bicycles.

So are we going to repeat indefinitely that energy doesn't come from nowhere?
If you're going to "suck" energy from any human activity, said humans will just have to produce more energy for the given task than if you didn't suck any. That's pretty simple.
Whether some people are OK with that - ask them. Sure, at least you're targetting gym settings, so yeah, machines have to resist human force anyway and that's wasted energy. You could replace that with something that actually uses the energy for something. That still doesn't mean everyone would be OK with it. Why so? Unless they get something back from that, many if not most people will prefer wasting their own energy rather than give it away for free to someone else, especially if this is for profit!

tom66 gave some figures (that IIRC seem to be in the right ballpark) that could give you an idea of what you could technically expect. And that's not very interesting, not even from an environment POV actually!

[Bud]

If people are smart enough to care about their health and go to gym, they would not eat burgers.

[FreddieChopin]

I remember we already talked about that on a topic about a startup? willing to do this kind ot thing to recharge batteries while people would be pedalling on bicycles.

So are we going to repeat indefinitely that energy doesn't come from nowhere?
If you're going to "suck" energy from any human activity, said humans will just have to produce more energy for the given task than if you didn't suck any. That's pretty simple.
Whether some people are OK with that - ask them. Sure, at least you're targetting gym settings, so yeah, machines have to resist human force anyway and that's wasted energy. You could replace that with something that actually uses the energy for something. That still doesn't mean everyone would be OK with it. Why so? Unless they get something back from that, many if not most people will prefer wasting their own energy rather than give it away for free to someone else, especially if this is for profit!

tom66 gave some figures (that IIRC seem to be in the right ballpark) that could give you an idea of what you could technically expect. And that's not very interesting, not even from an environment POV actually!

Honestly I also don't understand what's the point of wasting energy on a gym machine. If you drive a bike then at least you get to see countryside, maybe you'll find something cool (once after a rain I spotted 2 7.92x57 Mauser shells from 1938, fired from MG42 - so the place has history). Gym would be fun if it ended in strength exercise like that

[SiliconWizard]

Honestly I also don't understand what's the point of wasting energy on a gym machine. If you drive a bike then at least you get to see countryside, maybe you'll find something cool (once after a rain I spotted 2 7.92x57 Mauser shells from 1938, fired from MG42 - so the place has history).

Well, that's a fair point. You of course know the answer. It's all related to the way most of us live  - in a very sedentary manner. Many in cities in which what you describe is unfortunately not much of an option, or could even be unsafe. So people just exercise on machines instead, just to stay healthy. Well, in an attempt no to become too unhealthy anyway...

[tom66]

What about oil changes, timing belts, tyres, acid in batteries? I had my MTB for 12 years already and the only thing im changing is brakes and chain every 3 years. Everything else either broke years ago or doesnt need replacing.

I don't mean to deride cyclists - by all means please do cycle.

Just an interesting energy comparison - powering a 1.5-tonne petrol car is more efficient than a 150kg-human+bike, despite the car weighing 10x as much, if the cyclist eats a primarily meat-based diet. Maintenance is obviously excluded, annual oil changes and services probably do contribute some more emissions.

Vegans and vegetarians will do much better than meat eaters in terms of carbon emissions - it is just physics. Since if you eat a beef burger or beef products to cycle, there are three conversions: sunlight to grow crops, those crops fed to a cow, and that cow fed to a human then cycling under stress. So it is understandable that it is very lossy.

If you eat the crops directly (e.g. plant based diet) then cycling is probably better than a petrol car but an electric car is probably still better.  A cyclist eating just chicken is probably about the same as a petrol car, as chicken is much more efficient than beef.

This website says vegan burgers produce 10% of the emissions of regular beef burgers. (https://www.plantbasednews.org/lifestyle/vegan-beyond-burger-more-sustainable-beef) That puts the veggie burger cyclist at about half the emissions per km of that of the petrol car, but still about twice as much an electric car per km on UK electricity.

Probably the best option here is an e-bike or e-scooter; little human energy input but also much less electrical energy required to power it.  But then you don't get fit! 

[Seekonk]

Most people at a gym can't do 50W.

[Mr. Scram]

Who eats a primarily meat based diet? Even the meat centric US doesn't seem to manage that. Of course just proteins and fats won't properly sustain a human. You need carbohydrates to burn and those tend to come from plants. Note that this is mainstream medical and dietary knowledge. If you make different choices or have different beliefs that's for another thread

[Mr. Scram]

I don't mean to deride cyclists - by all means please do cycle.

Just an interesting energy comparison - powering a 1.5-tonne petrol car is more efficient than a 150kg-human+bike, despite the car weighing 10x as much, if the cyclist eats a primarily meat-based diet. Maintenance is obviously excluded, annual oil changes and services probably do contribute some more emissions.

Vegans and vegetarians will do much better than meat eaters in terms of carbon emissions - it is just physics. Since if you eat a beef burger or beef products to cycle, there are three conversions: sunlight to grow crops, those crops fed to a cow, and that cow fed to a human then cycling under stress. So it is understandable that it is very lossy.

If you eat the crops directly (e.g. plant based diet) then cycling is probably better than a petrol car but an electric car is probably still better.  A cyclist eating just chicken is probably about the same as a petrol car, as chicken is much more efficient than beef.

This website says vegan burgers produce 10% of the emissions of regular beef burgers. (https://www.plantbasednews.org/lifestyle/vegan-beyond-burger-more-sustainable-beef) That puts the veggie burger cyclist at about half the emissions per km of that of the petrol car, but still about twice as much an electric car per km on UK electricity.

Probably the best option here is an e-bike or e-scooter; little human energy input but also much less electrical energy required to power it.  But then you don't get fit!

Where's your calculation? The few sources I find seem to conclude that the impact of cycling is about a tenth of driving a car per distance. Some diets can indeed be worse than others but you obviously also tend to drive further than cycle.

https://ecf.com/files/wp-content/uploads/ECF_BROCHURE_EN_planche.pdf

[DenCraw]

"Vegans and vegetarians will do much better than meat eaters in terms of carbon emissions"
Quote from: tom66 on Yesterday at 09:05:07 pm

Well that is a strange statement.
I am in a Healty Keto diet since April and besides  went down to 73Kg from 87, from my previous believes on carb diet, my blood constants, liver levels, kidneys, are perfect as 20 years ago!.
The amount of intake calories are compose of 70% FAT, 20% Protein and 10%Carbs. I do OMAD, one meal a day, doing exercise and as a bonus, i produce less CO2 than the vegans.
The navy seal are adopting this diet.

But the point is, given that the people, here in Spain, are going massively to the gym, I thought that it is worth to recover that energy for doing something useful.

[tom66]

I don't mean to deride cyclists - by all means please do cycle.

Just an interesting energy comparison - powering a 1.5-tonne petrol car is more efficient than a 150kg-human+bike, despite the car weighing 10x as much, if the cyclist eats a primarily meat-based diet. Maintenance is obviously excluded, annual oil changes and services probably do contribute some more emissions.

Vegans and vegetarians will do much better than meat eaters in terms of carbon emissions - it is just physics. Since if you eat a beef burger or beef products to cycle, there are three conversions: sunlight to grow crops, those crops fed to a cow, and that cow fed to a human then cycling under stress. So it is understandable that it is very lossy.

If you eat the crops directly (e.g. plant based diet) then cycling is probably better than a petrol car but an electric car is probably still better.  A cyclist eating just chicken is probably about the same as a petrol car, as chicken is much more efficient than beef.

This website says vegan burgers produce 10% of the emissions of regular beef burgers. (https://www.plantbasednews.org/lifestyle/vegan-beyond-burger-more-sustainable-beef) That puts the veggie burger cyclist at about half the emissions per km of that of the petrol car, but still about twice as much an electric car per km on UK electricity.

Probably the best option here is an e-bike or e-scooter; little human energy input but also much less electrical energy required to power it.  But then you don't get fit!

Where's your calculation? The few sources I find seem to conclude that the impact of cycling is about a tenth of driving a car per distance. Some diets can indeed be worse than others but you obviously also tend to drive further than cycle.

https://ecf.com/files/wp-content/uploads/ECF_BROCHURE_EN_planche.pdf

As above in post #1 though I did assume the cyclist only ate beef, which as Scram mentioned is unusual, although I do know some people whose diet is probably 80% meat (in calorific value).

1kg beef produces 36kg CO2 - source https://www.theguardian.com/environment/2007/jul/19/climatechange.climatechange
A quarter pounder burger weighs 113g (duh), effectively produces 4.06kg CO2e and has a calorific value of ~225kcal https://www.myfitnesspal.com/food/calories/112885313

So 1kcal = 18g CO2.  50kcal per mile for an average cyclist, 1 mile = 904g CO2 = ~560gCO2/km

Quick calculation. A cyclist burns about 50 kcal per mile. A quarter pounder beef burger is 225 kcal so one burger = 4.5 miles or 7.2 km of cycling.  Roughly 36 kg of CO2e is produced or negatively offset, in the production of 1 kg of beef, so our burger costs us about 3.6 kg of CO2e.  7.2 km on 3.6 kg of CO2e is about 500gkm/CO2e.

I would be interested to see what the figures look like for a more typical diet, as I really only did this as a thought experiment on how inefficient humans are at extracting energy from their food, especially if we eat an animal that has also had to do that conversion into muscle mass.

(I am a meat eater, for what it is worth, though I have reduced my diet to consist mostly of chicken with beef only once a fortnight.)

[martin1454]

When I use the crosstrainer or bike in the gym, im around 200W for 30min, so around 100Wh - If everybody did that, it would make a bit of power but nothing significant

[Zero999]

"Vegans and vegetarians will do much better than meat eaters in terms of carbon emissions"
Quote from: tom66 on Yesterday at 09:05:07 pm

Well that is a strange statement.
I am in a Healty Keto diet since April and besides  went down to 73Kg from 87, from my previous believes on carb diet, my blood constants, liver levels, kidneys, are perfect as 20 years ago!.
The amount of intake calories are compose of 70% FAT, 20% Protein and 10%Carbs. I do OMAD, one meal a day, doing exercise and as a bonus, i produce less CO2 than the vegans.
The navy seal are adopting this diet.

But the point is, given that the people, here in Spain, are going massively to the gym, I thought that it is worth to recover that energy for doing something useful.

I've done a similar diet before. It worked in the short term, but not for long. Five months is nothing. See what happens to your body after five years of that diet.

Yes it's true that sort of diet is bad for the environment. It takes much more energy and CO₂ emissions to grow plants, feed them to animals and eat the animals, rather than to just eat the plants in the first place. The only time it makes sense to eat animals, is in places, with lots of natural, non-nutritious vegetation (mountains, grasslands, tundra) and aren't suitable for agriculture, but it's not possible to sustain a large population density of humans. Even in those instances, it's often better to import food or use technology such as greenhouses or irrigation to grow crops, than eat meat.

I used to be overweight and slimmed down without changing my diet, which wasn't the problem in the first place. I just exercise lots and get the extra calories from plant based carbohydrates. I'm not vegetarian. I do eat meat, but it's not where I get my extra calories from, when I exercise.

Just an interesting energy comparison - powering a 1.5-tonne petrol car is more efficient than a 150kg-human+bike, despite the car weighing 10x as much, if the cyclist eats a primarily meat-based diet. Maintenance is obviously excluded, annual oil changes and services probably do contribute some more emissions.

Vegans and vegetarians will do much better than meat eaters in terms of carbon emissions - it is just physics. Since if you eat a beef burger or beef products to cycle, there are three conversions: sunlight to grow crops, those crops fed to a cow, and that cow fed to a human then cycling under stress. So it is understandable that it is very lossy.

How many people weigh 150kg? That's well over double my bodyweight and is very fat, even in the US!

I believe when people increase their activity levels, they get most of their extra calories from carbohydrates, rather than meat. I find when I'm really active, I tend to get cravings for bread, sugar, cake etc. not steak, fish, chicken etc. If someone starts cycling to work, rather than driving, I doubt they'll eat that much more meat, but more carbohydrates.

This website says vegan burgers produce 10% of the emissions of regular beef burgers. (https://www.plantbasednews.org/lifestyle/vegan-beyond-burger-more-sustainable-beef) That puts the veggie burger cyclist at about half the emissions per km of that of the petrol car, but still about twice as much an electric car per km on UK electricity.

And vegan burgers are probably an inefficient source of food, compared to basic carbohydrates such as potatoes, sugarbeat, wheat, oats etc.

Probably the best option here is an e-bike or e-scooter; little human energy input but also much less electrical energy required to power it.  But then you don't get fit! 

You're better growing a lot of your own food, which will also keep you fit!

EDIT:
How about all the pollution and emissions in making the battery, which is also difficult and currently not economical to recycle?

[tszaboo]

The thing is, you can modify a cycle in a gym to generate electricity. Just put a generator on it, and thats it. And it will be a huge waste of energy and resources, and never will be worthwhile.
Let's say you put a generator on a bike. And people use it 8 hours a day when the gym is open, and half the time it is used.
That 250W from the second post is not average output, it is peak output. I went on ECG where I had to do biking, at 250W-350W I was almost passing out after a while (which was the point of the test). On average you will get something like a 100W. That is 146KWh per year, if the gym is open every day.

One solar panel would generate you 200-300KWh per year.

[Mr. Scram]

Regardless of the CO₂ situation having people cycle more will inevitably lead to more carbon emissions. When people are healthier they live longer and need more care towards the end of their lives. The most environmental friendly human is dead. Leading a sedentary lifestyle is likely the best thing you can do for the environment.

[Gyro]

The thing is, you can modify a cycle in a gym to generate electricity. Just put a generator on it, and thats it. And it will be a huge waste of energy and resources, and never will be worthwhile.
Let's say you put a generator on a bike. And people use it 8 hours a day when the gym is open, and half the time it is used.
That 250W from the second post is not average output, it is peak output. I went on ECG where I had to do biking, at 250W-350W I was almost passing out after a while (which was the point of the test). On average you will get something like a 100W. That is 146KWh per year, if the gym is open every day.

One solar panel would generate you 200-300KWh per year.

Our new LG washing machine, purchased last week has an energy consumption rating of A+++ minus 30% (we really need to update that rating system!). The actual consumption figure is 132kWh/year, based on the 220 wash standard.

With regular strenuous visits to the gym, you would be able to wash your gym clothes, towels etc. (and those of a few other members) for free! 

[tszaboo]

The thing is, you can modify a cycle in a gym to generate electricity. Just put a generator on it, and thats it. And it will be a huge waste of energy and resources, and never will be worthwhile.
Let's say you put a generator on a bike. And people use it 8 hours a day when the gym is open, and half the time it is used.
That 250W from the second post is not average output, it is peak output. I went on ECG where I had to do biking, at 250W-350W I was almost passing out after a while (which was the point of the test). On average you will get something like a 100W. That is 146KWh per year, if the gym is open every day.

One solar panel would generate you 200-300KWh per year.

Our new LG washing machine, purchased last week has an energy consumption rating of A+++ minus 30% (we really need to update that rating system!). The actual consumption figure is 132kWh/year, based on the 220 wash standard.

With regular strenuous visits to the gym, you would be able to wash your gym clothes, towels etc. (and those of a few other members) for free! 

Or go to the well regularly and wash your clothes there.

[Zero999]

Regardless of the CO₂ situation having people cycle more will inevitably lead to more carbon emissions. When people are healthier they live longer and need more care towards the end of their lives. The most environmental friendly human is dead. Leading a sedentary lifestyle is likely the best thing you can do for the environment.

It depends on how much care they need and for how long. Someone with type 2 diabetes might need a lot of care from a relatively early age, compared to someone who's more fit and healthy and dies a few years later, but very quickly. Exercise is said to help avoid health problems such as dementia, which are very costly to treat. It's an interesting thought though.

[metrologist]

7.2 km on 3.6 kg of CO2e is about 500gkm/CO2e.

What is a gkm?

[martin1454]

7.2 km on 3.6 kg of CO2e is about 500gkm/CO2e.

What is a gkm?

Gram per Kilometer

G/Km

[amspire]

Average dissipation of an idle human is around 150 watts.

An average healthy male can output around 250 watts.

A professional athletic cyclist can output around 800 watts ~ 1000 watts in short bursts.

But the metabolic efficiency of a human is barely 20%.  If you feed the human from beef burgers, then it is probably much worse than powering things from a diesel generator.  From plants it is probably a little better.

Quick calculation. A cyclist burns about 50 kcal per mile. A quarter pounder beef burger is 225 kcal so one burger = 4.5 miles or 7.2 km of cycling.  Roughly 36 kg of CO2e is produced or negatively offset, in the production of 1 kg of beef, so our burger costs us about 3.6 kg of CO2e.  7.2 km on 3.6 kg of CO2e is about 500gkm/CO2e.

The best petrol cars are around 1/4 of that and electric cars even better, so cycling (powered by beef burgers) is worse for the environment than driving a petrol car.  Of course, vegans have moral superiority here.

The problems I have with vegans is that their moral superiority tends to be based on appalling science. There is actually very little good science supporting vegan diets - the scientific support for low carb/keto diets is far more robust at this stage. I have actually looked at the studies that some of the most prominent vegans are saying justifies their diet, and the studies they highlight to me as an engineer are very problematic studies. If anyone actually knows of any solid scientific research papers supporting the vegan diets over low carb diets, please let me know. I would love to see them.

The Standard American (Australian) diet is not supported by science at all. Since this fad diet has been foisted on the world in the 1980's, there has been a very dramatic worsening of health to the point it is now a major crisis. Healthcare will not be affordable in 10 years. In the case of the Australian diet, it is reviewed once in 10 years, and the last review (2013) was done by one person (a contractor) who studied about 12 topics in total. The budget for this 10 year review was something like 1/2 a million dollars. Prior to 2013, there had been 3 major metastudies that reviewed all the evidence on saturated fat and these studies clearly stated the result was that there is just no evidence anywhere of any health problem with saturated fat. In the Australian 2013 dietary guidelines, they actually said in the appendix that they deliberately did not look at any evidence on saturated fat as it wasn't going to change their minds. That is not evidence based science.

The argument that vegan diets are better for the planet are also very weak.

Pasture animals can be 100% energy neutral, fields do not have to be fertilised or plowed which preserves the pasture. Cows do not naturally eat diets of corn and other grains - it makes them diabetic. It makes the meat a health problem for humans - just as with eggs from grain fed chickens and meat from grain fed pigs. Basically, we need to move away from industrialised animal agriculture and go back to a more local sustainable agriculture. This would be totally feasible in places like Australia. Harder in the US and Northern Europe. You would have to use stored hay in winter rather then grain.

Low carb and keto diets are not high protein diets - the percentage of protein is no more then more then most standard diets, and typically people on low carb and keto diets eat about 500 to 1000 kcals less then they did on the standard diets - they feel full and do not want to eat as much as they used to. On the keto diet, it is very easy to eat only one meal a day, or to not eat for 3 days if you are not hungry. On a keto diet, when you do not eat, you often have more physical energy if your body has a good store of fat. I started bike riding last year at the age of 62 and I never get hungry or tired after a 50km ride - about the longest rides I am doing at the moment.

As an engineer looking at the biggest current killer - heart disease, the problem seems simple. Clogged arteries always involves oxidised LDL. It is the oxidisation of the LDL lipid particles that forces the macrophages in the artery walls to see it as a toxic substance and to absorb it. If the macrophages are not overwhelmed, the HDL can clean up this captured LDL material and remove it from the arteries. You have healthy arteries without any plaque buildup. When the macrophages are overwhelmed with oxidised LDL, they turn into the foam cells in the walls of arteries and die. This is the process that forms the plaque and that blocks the arteries. The thing that oxidises in LDL is polyunsaturated fats. It is not cholesterol, saturated fats or monounsaturated fats that start the oxidation. When Omega 6 polyunsaturated fats oxidise, the first step is they become a peroxide, and peroxides can oxidise anything. Polyunstaturated fats only come from the diet, and you only need a small amount in the diet. A few grams a day. You do not need or want LDL lipid particles crammed full of Omega 6 polyunsaturated fats unless you really enjoy the thrill of taking statins and the fun of visiting cardiologists.

Pasture fed beef fat is 2% Omega 6 and 1% Omega 3 polyunsaturated fats - almost perfect. The fats in human breast milk used to be 1% polyunsaturated fat but now it is over 10% polyunsaturated fat typically.

Richard.

[Zero999]

Low carb and keto diets are not high protein diets - the percentage of protein is no more then more then most standard diets, and typically people on low carb and keto diets eat about 500 to 1000 kcals less then they did on the standard diets - they feel full and do not want to eat as much as they used to. On the keto diet, it is very easy to eat only one meal a day, or to not eat for 3 days if you are not hungry. On a keto diet, when you do not eat, you often have more physical energy if your body has a good store of fat. I started bike riding last year at the age of 62 and I never get hungry or tired after a 50km ride - about the longest rides I am doing at the moment.

Low carb diets aren't healthy at all. They might be good if someone is living a very sedentary lifestyle, or is significantly overweight, but they're no good for healthy, active people. I've tried one before, when I was slightly overweight and it was horrible. The problem was too few calories, which messes your body up more, than too much. I suffered from constipation, poor skin condition and it eventually led be to develop an eating disorder, which took years to fully recover from and I didn't do anything drastic at the start. I followed a supposedly safe, low carb diet, but it slowly spiralled out of control.

Pasture animals can be 100% energy neutral, fields do not have to be fertilised or plowed which preserves the pasture.

But they emit a lot of methane, a potent greenhouse gas.

Basically, we need to move away from industrialised animal agriculture and go back to a more local sustainable agriculture. This would be totally feasible in places like Australia. Harder in the US and Northern Europe. You would have to use stored hay in winter rather then grain.

I agree with this, but it is simply not possible to provide the entire world with that much meat from pasture animals, because there isn't the land available. It makes more sense to simply grow plants and eat them instead.

Forget all that palaeo bullshit you've probably read. People only got fat relatively recently, long after the palaeolithic era. Look at what humans ate before the obesity epidemic and it certainly was far from a low carb diet. They did eat less meat, but also fewer processed foods and did a lot more too. If you examine the diets of those in countries with low obesity rates, you'll find they're not low carb and they have a more active lifestyle, than most people living in the US. The obesity problem is caused by lack of exercise, not just poor diet.

[SiliconWizard]

Very low-carb diets can indeed be pretty unhealthy in the long run. If you don't ingest enough carbs, you'll be burning fat, basically liberating ketones. And too high a level of ketones can be a very serious condition. https://en.wikipedia.org/wiki/Ketoacidosis

So of course, it's all a matter of balance, and sure, many people in rich countries just ingest way too much carbs. But going from one extreme to the other may be a pretty bad idea.