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Which macronutrient can singularly sustain you for the rest of your life?

Answered on September 12, 2014
Created April 25, 2012 at 9:55 PM

Hypothetically speaking, which of the three macronutrients fats/proteins/carbs could singularly sustain you for the rest of your life if at all? And why?

3b3a449b6705e9ec8b141d0bd07c1a64

(1489)

on April 28, 2012
at 10:03 PM

classic hahahahahah!!

1296f5fecd084f101d7c5fbe013f07eb

(1213)

on April 27, 2012
at 08:19 PM

Bothersome because it betrays a total lack of understanding of how the human body functions?

A31b063c5866c08aa9968a8f2f1e9949

(1721)

on April 26, 2012
at 07:35 PM

Anyone care to tell me why they're downvoting this?

8496289baf18c2d3e210740614dc9082

(1867)

on April 26, 2012
at 07:35 PM

They're just not all needed. There is no dietary need for carbohydrates in any biochemical or physiologic process in the human body. It's certainly the case that some foks, especially wiry people with high BMRs, tend to feel better with a bit more carbs in their diet; but even these folks (and I know, I'm one of 'em) can do just peachy with zero carbs, so long as they're taking in their fats and proteins responsibly. Glucose is utilized preferentially to ketones (when both are present) in only a small handful of cell populations.

78cb3c4f70de5db2adb52b6b9671894b

(5519)

on April 26, 2012
at 07:22 PM

Yes! Except that this was a guy who claimed he got all his nutrition from the sun and didn't need food, BUT a documentary crew caught him sneaking in some restaurant's dumpster, ha ha.

77877f762c40637911396daa19b53094

(78467)

on April 26, 2012
at 04:45 PM

Exactly what I was going to say.

3b3a449b6705e9ec8b141d0bd07c1a64

(1489)

on April 26, 2012
at 04:21 PM

http://nyc.barstoolsports.com/random-thoughts/swiss-woman-gives-up-food-and-water-to-go-on-a-sunlight-only-diet-promptly-dies/ like this?

82166cc32b6cf26de33b69f58fb583b1

on April 26, 2012
at 03:14 PM

I agree that rabbit starvation is impossible on a diet of supermarket foods. But it's possible on a diet of rabbits. :)

82166cc32b6cf26de33b69f58fb583b1

on April 26, 2012
at 03:10 PM

I agree that rabbit starvation is impossible on a diet of supermarket foods. But it's possible on a diet of rabbits when other foods aren't available. Obviously this doesn't happen very often in the modern world.

82166cc32b6cf26de33b69f58fb583b1

on April 26, 2012
at 03:08 PM

I agree that rabbit starvation is impossible on a diet of supermarket foods. But it's possible on a diet of rabbits. :) Or a diet of protein powder. In real life, in the modern world, a person would probably get such strong cravings for fat and carbs that the condition would be self-limiting.

96bf58d8c6bd492dc5b8ae46203fe247

(37227)

on April 26, 2012
at 03:00 PM

@mzrdnan, it was not my intent to be "smarmy" but if I was I was. Your question tickled my funny bone and I typed accordingly. I was grinning as I posted my response. No offense meant.

7d64d3988de1b0e493aacf37843c5596

(2861)

on April 26, 2012
at 01:04 PM

None could singularly sustain you for too extended of a period. If you only ate 100% protein you would eventually run into rabbit starvation. If you didn’t eat protein your body would deteriorate and your heart would eventually fail if your compromised immune system didn’t get you first.

82166cc32b6cf26de33b69f58fb583b1

on April 26, 2012
at 12:44 PM

You're right and your comment is funny but it's worth pointing out that healthy people could probably last a year and even longer on a diet of pure fat. I base this comment on the fact that obese people have fasted (no food of any kind) for over a year. Reference: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2495396/pdf/postmedj00315-0056.pdf

82166cc32b6cf26de33b69f58fb583b1

on April 26, 2012
at 12:43 PM

You're right and your comment is funny but it's worth pointing out that healthy people could probably last a year and even longer on a diet of pure fat. I base this comment on the fact that obese people have fasted (no food of any kind) for over a year. Reference: (Longest fast in the medical literature)[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2495396/pdf/postmedj00315-0056.pdf]

2e5dc29c61f97d335ffb990508424719

on April 26, 2012
at 12:28 PM

Snakki, I do not disagree. I read "need" as in "need to eat." You do not need to eat carbohydrates, there is no dietary requirement. That is what I am saying.

3b3a449b6705e9ec8b141d0bd07c1a64

(1489)

on April 26, 2012
at 06:13 AM

I love bulletproof coffee...genius...

3b3a449b6705e9ec8b141d0bd07c1a64

(1489)

on April 26, 2012
at 06:09 AM

I was just wondering if what possible to eat only one type of macronutrient, at all. I wasn't suggesting it should be done. Hence the "hypothetically speaking." People on here are starting to just get smarmy rather than answering questions for what they are...just questions!

4d8ad2f7c42197b98b6b5443a57a7fe2

(20)

on April 26, 2012
at 04:31 AM

John i would say carbohydrates are so important that our bodies have developed other ways to make glucose. Yes you don't need to digest them but without glucose there is no life.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on April 26, 2012
at 04:10 AM

It is extremely easy to eat your EFA requirements.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on April 26, 2012
at 04:07 AM

Since EFAs are harmful at high doses (PUFA oxidation), our bodies do not produce them.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on April 26, 2012
at 04:04 AM

I believe that our bodies have built in redundancies as a survival mechanism. Thus, glucose is so essential to life that your body will produce if you do not eat it. I am not saying go eat 30 bananas a day, but I am saying that glucose is necessary for life.

C326acd0ae246a39c5685f2ba72e3136

(1631)

on April 26, 2012
at 02:35 AM

Exactly.Besides.When you are totally " keto-adapted, fat-adapted , blah blah " You actually require less glucose than if you were to run on carbohydrate as your main source of fuel... Most veggies and fruit and been hybridized and messed with so that they have the poison bred out of them. For example. Wild lettuce. I'd like to see you eat that. You'll be knocked out for a few hours due to the substance in them. vegetables have natural defenses to keep you from eating them.... I think plants as medicine. (green juices and such ) and MEAT as REAL food. Meat is really the only complete food.

C326acd0ae246a39c5685f2ba72e3136

(1631)

on April 26, 2012
at 02:30 AM

No need for an attitude damn..

A31b063c5866c08aa9968a8f2f1e9949

(1721)

on April 26, 2012
at 01:26 AM

Even if that were the case-and I would argue an inherent, even if unknown, value in carbohydrates by virtue of their being present in quality whole-food sources (like vegetables)-I would stand by the first half of my answer: none of the macronutrients could singularly sustain a person. I am loath to summarily dismiss carbohydrates as unnecessary simply because our body has a process to develop glucose in the absence of its provision from carbohydrates. That, to me, seems more like a survival mechanism than evidence that carbohydrates are not needed. (Of course we can take advantage of that).

2e5dc29c61f97d335ffb990508424719

on April 26, 2012
at 12:43 AM

Carbohydrates are not an obligate nutrient and are NOT needed at all. Your body can make all the glucose it needs via gluconeogenesis.

2e5dc29c61f97d335ffb990508424719

on April 26, 2012
at 12:40 AM

Carbohydrates are not an obligate nutrient and are NOT needed at all.

6ba6dc54fccbb9e01a07595137cecfa2

(92)

on April 26, 2012
at 12:10 AM

Protein and fats are essential and must be part of the diet.The body will make glucose from fat and all is well.This is the paleo advantage. Carbs are not essential and in to high a dose will cause metabolic dysfunction.Go meat or go weak,tis the way it is.

Medium avatar

(10663)

on April 25, 2012
at 11:49 PM

@foreveryoung Maybe that's why it's NON-essential...? Because your body can make it from other sources. Unlike certain ESSENTIAL fatty acids which you need to have in your diet.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on April 25, 2012
at 11:21 PM

You do need glucose. It is so essential that your body will produce if you cannot find it from an exogenous source (food).

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on April 25, 2012
at 10:26 PM

this question is bothersome.

  • 3b3a449b6705e9ec8b141d0bd07c1a64

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12 Answers

best answer

4
A31b063c5866c08aa9968a8f2f1e9949

(1721)

on April 25, 2012
at 09:56 PM

None of them. They're all needed.

A31b063c5866c08aa9968a8f2f1e9949

(1721)

on April 26, 2012
at 07:35 PM

Anyone care to tell me why they're downvoting this?

4d8ad2f7c42197b98b6b5443a57a7fe2

(20)

on April 26, 2012
at 04:31 AM

John i would say carbohydrates are so important that our bodies have developed other ways to make glucose. Yes you don't need to digest them but without glucose there is no life.

2e5dc29c61f97d335ffb990508424719

on April 26, 2012
at 12:28 PM

Snakki, I do not disagree. I read "need" as in "need to eat." You do not need to eat carbohydrates, there is no dietary requirement. That is what I am saying.

2e5dc29c61f97d335ffb990508424719

on April 26, 2012
at 12:40 AM

Carbohydrates are not an obligate nutrient and are NOT needed at all.

2e5dc29c61f97d335ffb990508424719

on April 26, 2012
at 12:43 AM

Carbohydrates are not an obligate nutrient and are NOT needed at all. Your body can make all the glucose it needs via gluconeogenesis.

A31b063c5866c08aa9968a8f2f1e9949

(1721)

on April 26, 2012
at 01:26 AM

Even if that were the case-and I would argue an inherent, even if unknown, value in carbohydrates by virtue of their being present in quality whole-food sources (like vegetables)-I would stand by the first half of my answer: none of the macronutrients could singularly sustain a person. I am loath to summarily dismiss carbohydrates as unnecessary simply because our body has a process to develop glucose in the absence of its provision from carbohydrates. That, to me, seems more like a survival mechanism than evidence that carbohydrates are not needed. (Of course we can take advantage of that).

8496289baf18c2d3e210740614dc9082

(1867)

on April 26, 2012
at 07:35 PM

They're just not all needed. There is no dietary need for carbohydrates in any biochemical or physiologic process in the human body. It's certainly the case that some foks, especially wiry people with high BMRs, tend to feel better with a bit more carbs in their diet; but even these folks (and I know, I'm one of 'em) can do just peachy with zero carbs, so long as they're taking in their fats and proteins responsibly. Glucose is utilized preferentially to ketones (when both are present) in only a small handful of cell populations.

best answer

3
82166cc32b6cf26de33b69f58fb583b1

on April 26, 2012
at 02:04 PM

Hypothetically speaking, which of the three macronutrients fats/proteins/carbs could singularly sustain you for the rest of your life if at all? And why?

As many people correctly pointed out, no single macronutrient will sustain a person for very long.

So let's change your question and ask, "If a person eats only a single macronutrient, what will happen?"

Fat. If a healthy adult eats only fat, he or she might live at least a year and even longer. I base this comment on the fact that obese people have fasted (no food) for over a year. A healthy person who eats only fat is like an obese person living off internal fat. The reason fat can sustain life so long is because under such conditions, the human body enters the natural state of extreme ketosis. Evolution has equipped our bodies with this ability to help us survive periods of starvation. In this state, our bodies make tremendous efforts to conserve micronutrients and protein and become very frugal in their use of glucose (in sustained, extreme ketosis the brain adapts by using ketones in place of some of the glucose that it normally consumes). A person on such a diet would gradually lose protein reserves (muscles and organs) and slowly lose bone (extreme ketosis demineralizes bone) but a person might live a fairly long time while these things occur.

Reference: Features of a successful therapeutic fast of 382 days' duration

Protein. A eucaloric diet of pure protein could not keep a person alive as long as a pure-fat diet because it very quickly induces "rabbit starvation." Symptoms arise within about a week, according to Vilhjalmur Stefansson. I say "eucaloric" because the problem here is that protein is toxic in large amounts. Maybe, if a person ate only the amount of protein contained in a normal diet and nothing else (a hypocaloric pure-protein diet) he or she would live a fairly long time.

Reference: Stefansson, Vilhjalmur. Not By Bread Alone reprinted in The Fat of the Land (1960), page 31

Carbs. A pure fat diet triggers the body's mechanisms for conserving micronutrients very quickly because such a diet simulates starvation, to which we are adapted by evolution. But a pure-carb diet might not have this same effect, at least not as quickly. Therefore I suspect a pure carb diet would not keep a person alive as long as a pure fat diet. On the other hand, unlike a pure protein diet, which is toxic, a pure fat carb diet is not toxic. Therefore I speculate that a pure carb diet would sustain life longer than pure protein but not as long as pure fat.

4
9f54852ea376e8e416356f547611e052

(2957)

on April 26, 2012
at 10:23 AM

Any one of them. Note that "rest of your life" will be short.

82166cc32b6cf26de33b69f58fb583b1

on April 26, 2012
at 12:44 PM

You're right and your comment is funny but it's worth pointing out that healthy people could probably last a year and even longer on a diet of pure fat. I base this comment on the fact that obese people have fasted (no food of any kind) for over a year. Reference: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2495396/pdf/postmedj00315-0056.pdf

77877f762c40637911396daa19b53094

(78467)

on April 26, 2012
at 04:45 PM

Exactly what I was going to say.

82166cc32b6cf26de33b69f58fb583b1

on April 26, 2012
at 12:43 PM

You're right and your comment is funny but it's worth pointing out that healthy people could probably last a year and even longer on a diet of pure fat. I base this comment on the fact that obese people have fasted (no food of any kind) for over a year. Reference: (Longest fast in the medical literature)[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2495396/pdf/postmedj00315-0056.pdf]

4
C326acd0ae246a39c5685f2ba72e3136

on April 25, 2012
at 11:18 PM

You don't need carbs. So you could definitely sustain yourself on 70-80 % calories from fat and the rest from protein.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on April 26, 2012
at 04:10 AM

It is extremely easy to eat your EFA requirements.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on April 25, 2012
at 11:21 PM

You do need glucose. It is so essential that your body will produce if you cannot find it from an exogenous source (food).

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on April 26, 2012
at 04:04 AM

I believe that our bodies have built in redundancies as a survival mechanism. Thus, glucose is so essential to life that your body will produce if you do not eat it. I am not saying go eat 30 bananas a day, but I am saying that glucose is necessary for life.

Medium avatar

(10663)

on April 25, 2012
at 11:49 PM

@foreveryoung Maybe that's why it's NON-essential...? Because your body can make it from other sources. Unlike certain ESSENTIAL fatty acids which you need to have in your diet.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on April 26, 2012
at 04:07 AM

Since EFAs are harmful at high doses (PUFA oxidation), our bodies do not produce them.

C326acd0ae246a39c5685f2ba72e3136

(1631)

on April 26, 2012
at 02:35 AM

Exactly.Besides.When you are totally " keto-adapted, fat-adapted , blah blah " You actually require less glucose than if you were to run on carbohydrate as your main source of fuel... Most veggies and fruit and been hybridized and messed with so that they have the poison bred out of them. For example. Wild lettuce. I'd like to see you eat that. You'll be knocked out for a few hours due to the substance in them. vegetables have natural defenses to keep you from eating them.... I think plants as medicine. (green juices and such ) and MEAT as REAL food. Meat is really the only complete food.

2
3846a3b61bc9051e4baebdef62e58c52

(18635)

on April 26, 2012
at 03:59 AM

fats and protein obviously....you need both

2
78cb3c4f70de5db2adb52b6b9671894b

on April 25, 2012
at 11:06 PM

Sunlight (from sungazing).

Just kidding. I'm just remembering a post here about how a guy got all his nutrients (no food) for months from the sun...

3b3a449b6705e9ec8b141d0bd07c1a64

(1489)

on April 26, 2012
at 04:21 PM

http://nyc.barstoolsports.com/random-thoughts/swiss-woman-gives-up-food-and-water-to-go-on-a-sunlight-only-diet-promptly-dies/ like this?

78cb3c4f70de5db2adb52b6b9671894b

(5519)

on April 26, 2012
at 07:22 PM

Yes! Except that this was a guy who claimed he got all his nutrition from the sun and didn't need food, BUT a documentary crew caught him sneaking in some restaurant's dumpster, ha ha.

3b3a449b6705e9ec8b141d0bd07c1a64

(1489)

on April 28, 2012
at 10:03 PM

classic hahahahahah!!

2
276d02485252b647c1ad4d8fe9857d8d

on April 25, 2012
at 11:03 PM

A family of goats

1
7fb4e9fb1162999cdd5099fee49dd0a7

on April 26, 2012
at 02:40 PM

Hmm... if we're saying hypothetically - as in, it's not the reality, but if it were - then I'd have to go with proteins. I like the texture, I like the flavor. Fats have better flavor but I know it would get overkill, fast. It's just too rich. I ate some ox tail the other day and the fat in that had me laid out after 3 pieces (I can normally go the whole hog on meat haha).

1
96bf58d8c6bd492dc5b8ae46203fe247

(37227)

on April 26, 2012
at 02:25 AM

Before asking this question you are required to reduce your wardrobe to one change of clothing. You are also required to have only one pair of shoes. You can watch only one TV program and you are limited to one website.

If your one website happens to be PH let me know and I'll try to come up with that one all-essential food. In the meantime, though, I'll continue to eat all the unprocessed foods I like while rotating my varied wardrobe, watching many sporting events and browsing the web.

C326acd0ae246a39c5685f2ba72e3136

(1631)

on April 26, 2012
at 02:30 AM

No need for an attitude damn..

96bf58d8c6bd492dc5b8ae46203fe247

(37227)

on April 26, 2012
at 03:00 PM

@mzrdnan, it was not my intent to be "smarmy" but if I was I was. Your question tickled my funny bone and I typed accordingly. I was grinning as I posted my response. No offense meant.

3b3a449b6705e9ec8b141d0bd07c1a64

(1489)

on April 26, 2012
at 06:09 AM

I was just wondering if what possible to eat only one type of macronutrient, at all. I wasn't suggesting it should be done. Hence the "hypothetically speaking." People on here are starting to just get smarmy rather than answering questions for what they are...just questions!

1
E55906cdb6839a23fd740ad85d160cc8

(1159)

on April 25, 2012
at 10:28 PM

Agreed. So I'll have my life sustaining barbecue, chocolate covered strawberries, and bulletproof coffee.

3b3a449b6705e9ec8b141d0bd07c1a64

(1489)

on April 26, 2012
at 06:13 AM

I love bulletproof coffee...genius...

0
6ec8d30130a6fb274871314533b5536b

(581)

on April 27, 2012
at 06:06 PM

Well, if you're eating animals, fat and protein are always together. One can survive on animal alone, some argue, but will not thrive. So, fat & protein would be the macronutrient to choose.

0
8496289baf18c2d3e210740614dc9082

on April 26, 2012
at 02:44 PM

RobS is pretty spot-on. Certain fats are essential: the body requires them for life and cannot metabolically produce them. Certain amino acids (protein) are essential: same deal, i.e. the definition of "essential." The only carbohydrate required for life is glucose, and that only in small amounts; but we can make far more than we need via gluconeogenesis. Ketosis handles the rest of what we need for energy, as ketones are actually the preferred fuel source (regardless of what we're taught) for most cells.

He's also right that pure fat would keep us alive longest and pure protein the shortest. But it would be so difficult to take in pure protein without fat that "rabbit starvation" is unlikely. What seems to kill folks so quickly in rabbit starvation is the lack of satiety: not feeling full, they pump their bodies far more full of lean meat than the liver/kidneys can handle. I /suspect/ that if one were to take several weeks of slowly increasing protein intake beyond the 200-300g/day the body can normally handle, and build also one's tolerance for the lack of satiety signaling from the hypothalamus, one could survive much longer.

82166cc32b6cf26de33b69f58fb583b1

on April 26, 2012
at 03:10 PM

I agree that rabbit starvation is impossible on a diet of supermarket foods. But it's possible on a diet of rabbits when other foods aren't available. Obviously this doesn't happen very often in the modern world.

82166cc32b6cf26de33b69f58fb583b1

on April 26, 2012
at 03:08 PM

I agree that rabbit starvation is impossible on a diet of supermarket foods. But it's possible on a diet of rabbits. :) Or a diet of protein powder. In real life, in the modern world, a person would probably get such strong cravings for fat and carbs that the condition would be self-limiting.

82166cc32b6cf26de33b69f58fb583b1

on April 26, 2012
at 03:14 PM

I agree that rabbit starvation is impossible on a diet of supermarket foods. But it's possible on a diet of rabbits. :)

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