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?
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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. |
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Any one of them. Note that "rest of your life" will be short. |
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None of them. They're all needed. |
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You don't need carbs. So you could definitely sustain yourself on 70-80 % calories from fat and the rest from protein. |
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A family of goats |
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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... |
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fats and protein obviously....you need both |
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Agreed. So I'll have my life sustaining barbecue, chocolate covered strawberries, and bulletproof coffee. |
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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. |
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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). |
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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. |
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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. |
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