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Is fasting supposed to work just due to going into a caloric hole, or is there also a time component to it? In other words: does a 6 hour run/hike on an empty s

Is fasting supposed to work just due to going into a caloric hole, or is there also a time component to it? In other words: does a 6 hour run/hike on an empty stomach where I burn 4000 Calories have the same effect as fasting for 36 hours?

rsync 8y ago
This is a good question - and it is not exactly the same question as "how long should I fast". You're trying to put your body in a state where it no longer has the resources to support extraneous energy consumers so a too-short fast will not work if you don't cross that threshold of bodily parsimony. I personally would hope that 16 hour IF-style fasts would be enough (because that's what I typically do), but I bet they're not ... But my parents question is a bit different: can one speed up the clock on the fast by burning through a lot of bodily resources through physical work. I suspect the answer is yes, to a degree - but I'll bet cancer cells are not in the same category of energy consumers as your muscles are - I'll bet there is a reserve of energy for them that doesn't get touched for a while, even if you do the big hike. It would be nice if there were some kind of threshold indicator that you could test for to see when your body as in a state of parsimony with regard to cancer cells ...
- 738472527784 8y ago
  A nightly fasting window of at least 13h has been shown to reduce recurrence of breast cancer in women.
yazaddaruvala 8y ago
Disclaimer: This is all speculation based on anecdata from the internets. Noone really knows if/why IF helps. Its not exactly the same. One is caloric restriction, and the other is caloric exhaustion. If your entire body worked as a single unit it might be that simple, but: 1. IF helps cull gut-bacteria which can only survive on simple foods. e.g. Bacteria which are inefficient and would happily produce toxins because it knows with enough of its simple foods it can outlive other populations and its own toxins. 2. IF helps turn off the digestive system. When this happens your stomach will stop "growling", and you will feel energetic even tho you haven't eated food for 16+ hours. Allowing the digestive system to relax, and flush/hopefully clean itself up, and won't happen because you went for a run. 3. Senesent/Cancerous cells may still be starved by exhausting all calories quickly, but it really depends on how those cells die(it might just take time), and how the body allocates resources. You can imagine a tumor sitting on a major blood vessel will continue to eat before any muscles are. The only way to starve it is to not eat. All that said, exercise is always good. Just be careful. Try to do it in the first half rather than the second half of your fast. Fainting is never good.
- logfromblammo 8y ago
  Despite your concluding statement, there is something called "bonk training". Basically, you exhaust your glycogen stores as much as possible before beginning your workout. So when you start running/biking, your body is in a similar state to just after hitting the wall in a marathon or several hours into a long bike race or triathlon without eating. Since you have insufficient glycogen, you just can't do more than 70% your max heart rate. It is reputed to produce advantageous training adaptations when done in addition to normal training. But if you aren't on a keto diet already, that sounds like a great way to simulate the worst tortures of Hell. You probably won't even be able to push yourself hard enough to faint, but you will wish you had. There's a good reason racers down that glycogen gel stuff during their endurance races now.
  - 738472527784 8y ago
    Anecdotally, I'd like to add that I run much better fasted than not. Granted I only run for 30 to 60 min, but even up to 36 hours fasting did not make it harder at all. I feel lighter, euphoric and my motivation does not change over the time running. Though, I speculate that running in the beginning of your fasting window will increase the time of glucose depletion and maaaybe make the fasting more efficient. Though, repairing exercise induced injuries probably won't be efficient.
nradov 8y ago
Is that a realistic example? Very few people including trained athletes would actually be able to expend 4000kcal in 6 hours without some nutrition. After the immediate glycogen stores are depleted in a couple hours your power output drops dramatically if you don't consume anything.
- raarts 8y ago
  Unless you’re keto adapted that is (i.e. being in ketosis for a couple of weeks). When you're keto-adapted your body is used to running on your fat, and you won't experience 'bonking'.
- buzzdenver 8y ago
  Today I just did a strenuous 4-hour hike on an empty stomach which based on my weight was about 2500-3000 calories. I drank about 100 calories worth of Gatorade, and I don't do any special diets. Just years of long runs/hikes.
738472527784 8y ago
I am just one of those internet health "scientists", check some keywords of what I am saying for yourself. There is no conclusive data on all nutrition/eating habits. People like me gamble against the supposed average. Sometimes these hypes have been shown to be in fact detrimental (see antioxidant supplementation and cancer risk). To your question: I doubt it's the same as many speculated mechanisms of fasting benefits are tied to your body's usual maintenance workings which just require some time. I suspect that some mechanisms are tied to a "low glucose signal", but the majority are things which are always present, but get interrupted or are less efficient when digestion is triggered and nutrients flood the blood stream. Example 1: Glucose and complete (animal/soy isolate) protein trigger steady, increased IGF-1 secretion, which translates to "oh boy this is good, grow everything, store everything, who knows when we get something like this again. Noo, no maintenance! Build!". Higher IGF-1 levels are linked to cancer. Less nutritional "efficient" diets, like plant based, vegan diets are linked to an decreased cancer risk. Example 2: Autophagy is always done (although increased when fasting), it's not hard to imagine the results to be much more protective when the garbage collection comes out ahead of the trash production from time to time. Mind that one problem with cancerous cells is the cloaking, hiding from the immune system, which might be done by accumulation of extracellular trash through increased cellular metabolism. Cleaning this up, might help the immune cells to target and kill cancer and precancerous cells. Since eating became always accessible pleasure, I speculate some metabolic expectations of the body to be not met and humans tend to be in constant celebration mode. It's worth noting that cancer is naturally a rare event and absolutely linked to life style changes in humans and toxic byproducts of human civilization for all animals.
- 738472527784 8y ago
  I want to add: plant based diets are associated with something like a 10% (or more) decrease in overall cancer risk, which doesn't seem like a lot, BUT the average life time risk to DIE because of cancer is 1:5, so really fucking high.

rsync 8y ago

This is a good question - and it is not exactly the same question as "how long should I fast". You're trying to put your body in a state where it no longer has the resources to support extraneous energy consumers so a too-short fast will not work if you don't cross that threshold of bodily parsimony. I personally would hope that 16 hour IF-style fasts would be enough (because that's what I typically do), but I bet they're not ... But my parents question is a bit different: can one speed up the clock on the fast by burning through a lot of bodily resources through physical work. I suspect the answer is yes, to a degree - but I'll bet cancer cells are not in the same category of energy consumers as your muscles are - I'll bet there is a reserve of energy for them that doesn't get touched for a while, even if you do the big hike. It would be nice if there were some kind of threshold indicator that you could test for to see when your body as in a state of parsimony with regard to cancer cells ...

738472527784 8y ago
A nightly fasting window of at least 13h has been shown to reduce recurrence of breast cancer in women.

yazaddaruvala 8y ago

Disclaimer: This is all speculation based on anecdata from the internets. Noone really knows if/why IF helps. Its not exactly the same. One is caloric restriction, and the other is caloric exhaustion. If your entire body worked as a single unit it might be that simple, but: 1. IF helps cull gut-bacteria which can only survive on simple foods. e.g. Bacteria which are inefficient and would happily produce toxins because it knows with enough of its simple foods it can outlive other populations and its own toxins. 2. IF helps turn off the digestive system. When this happens your stomach will stop "growling", and you will feel energetic even tho you haven't eated food for 16+ hours. Allowing the digestive system to relax, and flush/hopefully clean itself up, and won't happen because you went for a run. 3. Senesent/Cancerous cells may still be starved by exhausting all calories quickly, but it really depends on how those cells die(it might just take time), and how the body allocates resources. You can imagine a tumor sitting on a major blood vessel will continue to eat before any muscles are. The only way to starve it is to not eat. All that said, exercise is always good. Just be careful. Try to do it in the first half rather than the second half of your fast. Fainting is never good.

logfromblammo 8y ago
Despite your concluding statement, there is something called "bonk training". Basically, you exhaust your glycogen stores as much as possible before beginning your workout. So when you start running/biking, your body is in a similar state to just after hitting the wall in a marathon or several hours into a long bike race or triathlon without eating. Since you have insufficient glycogen, you just can't do more than 70% your max heart rate. It is reputed to produce advantageous training adaptations when done in addition to normal training. But if you aren't on a keto diet already, that sounds like a great way to simulate the worst tortures of Hell. You probably won't even be able to push yourself hard enough to faint, but you will wish you had. There's a good reason racers down that glycogen gel stuff during their endurance races now.
- 738472527784 8y ago
  Anecdotally, I'd like to add that I run much better fasted than not. Granted I only run for 30 to 60 min, but even up to 36 hours fasting did not make it harder at all. I feel lighter, euphoric and my motivation does not change over the time running. Though, I speculate that running in the beginning of your fasting window will increase the time of glucose depletion and maaaybe make the fasting more efficient. Though, repairing exercise induced injuries probably won't be efficient.

nradov 8y ago

Is that a realistic example? Very few people including trained athletes would actually be able to expend 4000kcal in 6 hours without some nutrition. After the immediate glycogen stores are depleted in a couple hours your power output drops dramatically if you don't consume anything.

raarts 8y ago
Unless you’re keto adapted that is (i.e. being in ketosis for a couple of weeks). When you're keto-adapted your body is used to running on your fat, and you won't experience 'bonking'.
buzzdenver 8y ago
Today I just did a strenuous 4-hour hike on an empty stomach which based on my weight was about 2500-3000 calories. I drank about 100 calories worth of Gatorade, and I don't do any special diets. Just years of long runs/hikes.

738472527784 8y ago

I am just one of those internet health "scientists", check some keywords of what I am saying for yourself. There is no conclusive data on all nutrition/eating habits. People like me gamble against the supposed average. Sometimes these hypes have been shown to be in fact detrimental (see antioxidant supplementation and cancer risk). To your question: I doubt it's the same as many speculated mechanisms of fasting benefits are tied to your body's usual maintenance workings which just require some time. I suspect that some mechanisms are tied to a "low glucose signal", but the majority are things which are always present, but get interrupted or are less efficient when digestion is triggered and nutrients flood the blood stream. Example 1: Glucose and complete (animal/soy isolate) protein trigger steady, increased IGF-1 secretion, which translates to "oh boy this is good, grow everything, store everything, who knows when we get something like this again. Noo, no maintenance! Build!". Higher IGF-1 levels are linked to cancer. Less nutritional "efficient" diets, like plant based, vegan diets are linked to an decreased cancer risk. Example 2: Autophagy is always done (although increased when fasting), it's not hard to imagine the results to be much more protective when the garbage collection comes out ahead of the trash production from time to time. Mind that one problem with cancerous cells is the cloaking, hiding from the immune system, which might be done by accumulation of extracellular trash through increased cellular metabolism. Cleaning this up, might help the immune cells to target and kill cancer and precancerous cells. Since eating became always accessible pleasure, I speculate some metabolic expectations of the body to be not met and humans tend to be in constant celebration mode. It's worth noting that cancer is naturally a rare event and absolutely linked to life style changes in humans and toxic byproducts of human civilization for all animals.

738472527784 8y ago
I want to add: plant based diets are associated with something like a 10% (or more) decrease in overall cancer risk, which doesn't seem like a lot, BUT the average life time risk to DIE because of cancer is 1:5, so really fucking high.