Fasted running

13

Replies

  • gobonas99
    gobonas99 Posts: 1,049 Member
    Just eat a banana and go. You might feel hungry, but you're not gonna die. One could theoretically go an entire marathon on a banana, just sayin.

    I'm saying the opposite, I don't get hungry before and if I eat anything, even a banana, I hurl.

    I'm not seeing the problem :)

    However, I thought you said something about eating eggs or a protein shake. Those are slow digesting and would absolutely give you stomach crap on a run. On my weekday runs, I go around 11am, so yes I do eat before. Usually 3 eggs at 7, and a banana at 830 and oatmeal at 9-930.

    I was just wondering if I'm making things harder for myself by not eating, maybe my performance would be better if I ate? maybe I'm supposed to eat and I'm a freak of nature for getting an upset stomach?

    For the short distances that you're doing, not eating anything before your run isn't going to affect anything. :smile: I know for short distances, I actually feel better when I don't eat first (and my times show it) :happy:
  • likitisplit
    likitisplit Posts: 9,420 Member
    Short distance runs like that are fine. If you feel weak or tired during the run, try some gatorade or other sports drink.
  • SonicDeathMonkey80
    SonicDeathMonkey80 Posts: 4,489 Member
    Just eat a banana and go. You might feel hungry, but you're not gonna die. One could theoretically go an entire marathon on a banana, just sayin.

    I'm saying the opposite, I don't get hungry before and if I eat anything, even a banana, I hurl.

    I'm not seeing the problem :)

    However, I thought you said something about eating eggs or a protein shake. Those are slow digesting and would absolutely give you stomach crap on a run. On my weekday runs, I go around 11am, so yes I do eat before. Usually 3 eggs at 7, and a banana at 830 and oatmeal at 9-930.

    I was just wondering if I'm making things harder for myself by not eating, maybe my performance would be better if I ate? maybe I'm supposed to eat and I'm a freak of nature for getting an upset stomach?

    Like I said, you're doing fine. Everyone is different, and your body may or may not change, depending on your mileage and "rungries." Sometimes I will eat a slice of pizza and run, other times it's a sip of water. Once, I ate 22 donut holes and ran 4 miles, throwing up 3.5 into it. Heck, on Friday, I ate an apple and ran and had the worst stomach cramps and side stitches. It's trial and error, and there really isn't a right or wrong way.
  • litsy3
    litsy3 Posts: 783 Member
    I'm an experiment of one, but I do ALL of my running in a fasted state. I've done 90+ mile weeks with 22 mile long runs in a fasted state. I didn't bonk, lose muscle mass or anything else. It works just fine for me. You'll just have to try it and see.

    Me too. Except the 90+ mile weeks. Never done those!

    Oh, and I have breakfast three hours before a race. And occasionally I have to run in the evening, in which case I have a mid-afternoon snack. But otherwise I just do all my runs - long, short, fast, whatever - before breakfast. Otherwise I'd have to get up WAY earlier than I'd like.
  • DavidMartinez2
    DavidMartinez2 Posts: 840 Member
    The only time I eat or drink anything before I run is if I am racing something with "marathon" in the title and even then I try to eat 2-3 hours before hand to avoid stomach issues. A lot of people have GI problems when they run, your training will not suffer if you do your runs in a fasted state.
  • JustWant2Run
    JustWant2Run Posts: 286 Member
    I'm an experiment of one, but I do ALL of my running in a fasted state. I've done 90+ mile weeks with 22 mile long runs in a fasted state. I didn't bonk, lose muscle mass or anything else. It works just fine for me. You'll just have to try it and see.

    Me too. Except the 90+ mile weeks. Never done those!

    Oh, and I have breakfast three hours before a race. And occasionally I have to run in the evening, in which case I have a mid-afternoon snack. But otherwise I just do all my runs - long, short, fast, whatever - before breakfast. Otherwise I'd have to get up WAY earlier than I'd like.

    And I am the total opposite. I always eat before my runs... I usually don't fuel up during though, except for one long run in which I try to test my race day strategy including gels and water.

    And I didn't bonk or hit the wall in my one and only marathon because I've never run fasted!!

    Experiment, you will figure out what works for you.
  • Lofteren
    Lofteren Posts: 960 Member
    OK! Here is my skinny on fasted and unfasted running.

    First some fueling tips if you do decide to eat before running.

    Try different things. Different people react to different foods differently. You want to experiment in training runs so you know what works and doesn't work as you prepare for races. When you find something that works, you gonna want to replicate that before a race. This includes your day before pre-race meal.

    Eating too many calories before a run can lock up your stomach pretty bad and cause discomfort. As you run, blood is being diverted to the areas that require oxygen and liver glycogen and fat absorption during your run. This blood is diverted away from other functions such as digestion. I go by Runner's World Big Book of Marathon and HM Training. 600 calories approx 3 hours before a big run in simple carbs or 200 cals 1 hour before. As you are running, 100 cals 30 minutes into the run and 45 minutes thereafter.

    Why fuel up as you are running? As your body uses the anaerobic system (burning fuel without the presense of oxygen) you will be burning up your internal carb stores (glycogen). You have a limited supply. Different people have different levels and it depends how intense you run, but for most experienced runners, they should be able to run 15-20 miles and even beyond without worry of bonking (clearing out their glycogen supply). Running way beyond your aerobic threshold or poor training may cause you to bonk much sooner. The idea is to supplement the amount of glycogen you use up as you run but not replace it all together during the run. If you bonk too fast, then you are running faster than you should for your goal distance.

    If you run at a pace that is below your aerobic threshold (burning fuel in the presense of oxygen) then your fuel supply relies more on your internal fat storage as opposed to glycogen. Your body (in comparison to gycogen) has a virtual endless supply of fat to fuel long term activity.

    So this leads us into training and especially fasted training.

    If you have long steady training runs that you rely on your aerobic system, your body will begin to learn to rely more on fat burning as opposed to glycogen burning. Training fasted during these runs will slowly deplete your glycogen and will stimulate growth in this area. In other words, your body will soon learn to store more glycogen for future runs. As you sleep, your body begins to use up and lower your blood sugar. When your blood sugar goes below a certain point, it may either use fat or glycogen to fuel your bodies survival mechanisms as you sleep. If you train to rely on fat burning, your body will burn less glycogen but it will burn some glycogen none the less. So unless you eat something in the morning before you run, you will have diminished glycogen stores.

    This could be a good thing tho if you don't mind diminished performace in trade for stimulating growth.
    At a certain point, your body will experience diminished returns and poor performance will outweigh the benefits of stimulating the growth of glycogen storage. But in the beginning of the training season, the diminished supply of blood sugar and glycogen during fasted runs will take some getting used to as your body learns to power from your fat storage and aerobic system.

    If fasted running causes the body to learn to store more glycogen, it will become increasingly difficult to do fasted running, n'est-ce pas? ????

    I have actually read some conflicting physiology studies on this. Running (in general) especially in a fasted state burns more fat during exercise than other forms of exercise which up regulates production of fat mobilizing enzymes. This could be a good thing DURING your run; however, after the run the upregulation of these enzymes can make it easier for you to store fat. Whereas, stimulation of glycogen mobilizing enzymes would be best performed with anaerobic methods of training.
  • _Waffle_
    _Waffle_ Posts: 13,049 Member
    Fasted LISS? Sounds like a recipe for muscle loss and high cortisol levels.

    If your goals are centered around running then eat a healthy meal an hour or so before you run. If your goals are centered around body composition then eat a meal an hour before you train and stop running. Instead, lift weights and do HIIT. I would recommend a heavy bag, prowler, sledge hammer, kettlebell or a heavy carrying implement (this could just be a big rock) for your HIIT.

    c91KrQMl.jpg
  • Lofteren
    Lofteren Posts: 960 Member
    Fasted LISS? Sounds like a recipe for muscle loss and high cortisol levels.

    If your goals are centered around running then eat a healthy meal an hour or so before you run. If your goals are centered around body composition then eat a meal an hour before you train and stop running. Instead, lift weights and do HIIT. I would recommend a heavy bag, prowler, sledge hammer, kettlebell or a heavy carrying implement (this could just be a big rock) for your HIIT.

    c91KrQMl.jpg

    Makes jokes about training specific metabolic systems


    Has absolutely no argument, just a meme
  • ThickMcRunFast
    ThickMcRunFast Posts: 22,511 Member
    You're fine. Just go run.

    (and I usually run fasted as well. At most I'll have some toast or a banana, and that's only for runs over 10 miles. The only time I eat while running in training is during trail runs that are going to clock more than 3 hours)
  • rybo
    rybo Posts: 5,424 Member
    There is nothing wrong with your plan. In fact I think fasted long runs are a great training tool. I've gone up to 20 miles fasted and no gels during the runs. One fasted long run a week is not going to eat all your muscle either like some are trying to claim.
  • Carrieendar
    Carrieendar Posts: 493 Member
    these days I do:

    60-85 min runs- totally fasted
    90-120 min runs- meal 1.5 hours before, nothing on run
    120 + I do 50% fasted, 50% I take the same energy I use in race with me (30-50 g carbs per hour)-- when I do take in carbs on these long runs I use them as marathon simulation type runs.
    track work: I use carbs most of them time, in my experimenting with performance, I do better with carb intake
  • PwrLftr82
    PwrLftr82 Posts: 945 Member
    I have run a half marathon fasted--from what I have read you should be fine for fasted long runs until they get to the 18 mile plus distance. Our livers store lots of glycogen and our muscles carry some as well. How long are your morning fasted runs?

    I also can't eat then run. I have to have at least 3-4 hours after eating before I run, longer for large meals.

    Only 4-5 miles, but I have a 10k in November, so I'm currently working towards 6 miles and then further.

    I've run a marathon fasted as well as several halfs (and training runs). I can't handle any food before running.
  • sarahc001
    sarahc001 Posts: 477 Member
    I have been slowly building up my fasted training- last Thursday's trail run was from 10am-230pm and my only "meal" (at 5:30am) consisted of two shots of espresso and a cup of almond milk (about 40cal.)

    I have been doing this partially in response to (stupidly) forgetting to eat breakfast on my 100mi attempt, getting sick when I grabbed high fat food at mile 13, resulting in gastric distress, extreme slowdown, and a DNF at mile 75. I decided that I wanted to be prepared for whatever a race threw at me (or that I threw at myself lol) and am making sure that I can push through and train to be stronger under less than optimal conditions. An experiment of one, definitely, but this experiment is going well...proper fueling at my last race (sept 20) resulted in a PR of 52mi in 10:48 and the most even splits of any race thus far. A 6.5mi looped course, and my 8th (last) loop was actually faster than my 7th. Training fasted and fueling moderately (including eating breakfast) before and during a long race seems to be working.
  • MeanderingMammal
    MeanderingMammal Posts: 7,866 Member
    also, for a reduced noise level, I would recommend you check out the long distance running group..

    Agreed

    And to answer the original question, for my evening runs I'm comfortable doing 6-7 miles having not eaten for 6-7 hours, although I will have water for most of the afternoon.

    For longer than that, my weekend forenoon sessions, I'll generally have something like a bowl of porridge, or a couple of slices of wholemeal toast with banana an hour or so before going out the door.

    As I've conditioned myself to running I've become much more comfortable with less fuel and less water, over time.
  • Azdak
    Azdak Posts: 8,281 Member
    OK! Here is my skinny on fasted and unfasted running.

    First some fueling tips if you do decide to eat before running.

    Try different things. Different people react to different foods differently. You want to experiment in training runs so you know what works and doesn't work as you prepare for races. When you find something that works, you gonna want to replicate that before a race. This includes your day before pre-race meal.

    Eating too many calories before a run can lock up your stomach pretty bad and cause discomfort. As you run, blood is being diverted to the areas that require oxygen and liver glycogen and fat absorption during your run. This blood is diverted away from other functions such as digestion. I go by Runner's World Big Book of Marathon and HM Training. 600 calories approx 3 hours before a big run in simple carbs or 200 cals 1 hour before. As you are running, 100 cals 30 minutes into the run and 45 minutes thereafter.

    Why fuel up as you are running? As your body uses the anaerobic system (burning fuel without the presense of oxygen) you will be burning up your internal carb stores (glycogen). You have a limited supply. Different people have different levels and it depends how intense you run, but for most experienced runners, they should be able to run 15-20 miles and even beyond without worry of bonking (clearing out their glycogen supply). Running way beyond your aerobic threshold or poor training may cause you to bonk much sooner. The idea is to supplement the amount of glycogen you use up as you run but not replace it all together during the run. If you bonk too fast, then you are running faster than you should for your goal distance.

    If you run at a pace that is below your aerobic threshold (burning fuel in the presense of oxygen) then your fuel supply relies more on your internal fat storage as opposed to glycogen. Your body (in comparison to gycogen) has a virtual endless supply of fat to fuel long term activity.

    So this leads us into training and especially fasted training.

    If you have long steady training runs that you rely on your aerobic system, your body will begin to learn to rely more on fat burning as opposed to glycogen burning. Training fasted during these runs will slowly deplete your glycogen and will stimulate growth in this area. In other words, your body will soon learn to store more glycogen for future runs. As you sleep, your body begins to use up and lower your blood sugar. When your blood sugar goes below a certain point, it may either use fat or glycogen to fuel your bodies survival mechanisms as you sleep. If you train to rely on fat burning, your body will burn less glycogen but it will burn some glycogen none the less. So unless you eat something in the morning before you run, you will have diminished glycogen stores.

    This could be a good thing tho if you don't mind diminished performace in trade for stimulating growth.
    At a certain point, your body will experience diminished returns and poor performance will outweigh the benefits of stimulating the growth of glycogen storage. But in the beginning of the training season, the diminished supply of blood sugar and glycogen during fasted runs will take some getting used to as your body learns to power from your fat storage and aerobic system.

    If fasted running causes the body to learn to store more glycogen, it will become increasingly difficult to do fasted running, n'est-ce pas? ????

    I have actually read some conflicting physiology studies on this. Running (in general) especially in a fasted state burns more fat during exercise than other forms of exercise which up regulates production of fat mobilizing enzymes. This could be a good thing DURING your run; however, after the run the upregulation of these enzymes can make it easier for you to store fat. Whereas, stimulation of glycogen mobilizing enzymes would be best performed with anaerobic methods of training.

    The whole point of training, esp endurance running, is to train the body to optimally perform under certain specific conditions. Endurance training effects are meant to improve endurance performance--sometimes that does not coincide with other exercise goals such as weight loss or even overall health. Overall, the idea of doing fasted cardio for fat loss has been shown to be seriously flawed, if not outright debunked--but that's a different topic :smile:

    Glycogen sparing is obviously a good thing for endurance performance.

    Another point: a number of studies have shown that HIIT training can result in some of the same fat-burning adaptations as endurance training.This has lead to some people again trying to assert that HIIT training is a "one stop shop" that obviates the need for endurance training. However, every instinct of training and physiology says that you cannot train for a marathon by doing 20-min max interval training workouts, so I am looking forward to further research on this topic.
  • Lofteren
    Lofteren Posts: 960 Member
    OK! Here is my skinny on fasted and unfasted running.

    First some fueling tips if you do decide to eat before running.

    Try different things. Different people react to different foods differently. You want to experiment in training runs so you know what works and doesn't work as you prepare for races. When you find something that works, you gonna want to replicate that before a race. This includes your day before pre-race meal.

    Eating too many calories before a run can lock up your stomach pretty bad and cause discomfort. As you run, blood is being diverted to the areas that require oxygen and liver glycogen and fat absorption during your run. This blood is diverted away from other functions such as digestion. I go by Runner's World Big Book of Marathon and HM Training. 600 calories approx 3 hours before a big run in simple carbs or 200 cals 1 hour before. As you are running, 100 cals 30 minutes into the run and 45 minutes thereafter.

    Why fuel up as you are running? As your body uses the anaerobic system (burning fuel without the presense of oxygen) you will be burning up your internal carb stores (glycogen). You have a limited supply. Different people have different levels and it depends how intense you run, but for most experienced runners, they should be able to run 15-20 miles and even beyond without worry of bonking (clearing out their glycogen supply). Running way beyond your aerobic threshold or poor training may cause you to bonk much sooner. The idea is to supplement the amount of glycogen you use up as you run but not replace it all together during the run. If you bonk too fast, then you are running faster than you should for your goal distance.

    If you run at a pace that is below your aerobic threshold (burning fuel in the presense of oxygen) then your fuel supply relies more on your internal fat storage as opposed to glycogen. Your body (in comparison to gycogen) has a virtual endless supply of fat to fuel long term activity.

    So this leads us into training and especially fasted training.

    If you have long steady training runs that you rely on your aerobic system, your body will begin to learn to rely more on fat burning as opposed to glycogen burning. Training fasted during these runs will slowly deplete your glycogen and will stimulate growth in this area. In other words, your body will soon learn to store more glycogen for future runs. As you sleep, your body begins to use up and lower your blood sugar. When your blood sugar goes below a certain point, it may either use fat or glycogen to fuel your bodies survival mechanisms as you sleep. If you train to rely on fat burning, your body will burn less glycogen but it will burn some glycogen none the less. So unless you eat something in the morning before you run, you will have diminished glycogen stores.

    This could be a good thing tho if you don't mind diminished performace in trade for stimulating growth.
    At a certain point, your body will experience diminished returns and poor performance will outweigh the benefits of stimulating the growth of glycogen storage. But in the beginning of the training season, the diminished supply of blood sugar and glycogen during fasted runs will take some getting used to as your body learns to power from your fat storage and aerobic system.

    If fasted running causes the body to learn to store more glycogen, it will become increasingly difficult to do fasted running, n'est-ce pas? ????

    I have actually read some conflicting physiology studies on this. Running (in general) especially in a fasted state burns more fat during exercise than other forms of exercise which up regulates production of fat mobilizing enzymes. This could be a good thing DURING your run; however, after the run the upregulation of these enzymes can make it easier for you to store fat. Whereas, stimulation of glycogen mobilizing enzymes would be best performed with anaerobic methods of training.

    The whole point of training, esp endurance running, is to train the body to optimally perform under certain specific conditions. Endurance training effects are meant to improve endurance performance--sometimes that does not coincide with other exercise goals such as weight loss or even overall health. Overall, the idea of doing fasted cardio for fat loss has been shown to be seriously flawed, if not outright debunked--but that's a different topic :smile:

    Glycogen sparing is obviously a good thing for endurance performance.

    Another point: a number of studies have shown that HIIT training can result in some of the same fat-burning adaptations as endurance training.This has lead to some people again trying to assert that HIIT training is a "one stop shop" that obviates the need for endurance training. However, every instinct of training and physiology says that you cannot train for a marathon by doing 20-min max interval training workouts, so I am looking forward to further research on this topic.

    I agree that HIIT wouldn't be appropriate for a competitive long distance runner to focus a majority of their time on. The SAID principle always applies to sports specific training.
  • _Waffle_
    _Waffle_ Posts: 13,049 Member
    OK! Here is my skinny on fasted and unfasted running.

    First some fueling tips if you do decide to eat before running.

    Try different things. Different people react to different foods differently. You want to experiment in training runs so you know what works and doesn't work as you prepare for races. When you find something that works, you gonna want to replicate that before a race. This includes your day before pre-race meal.

    Eating too many calories before a run can lock up your stomach pretty bad and cause discomfort. As you run, blood is being diverted to the areas that require oxygen and liver glycogen and fat absorption during your run. This blood is diverted away from other functions such as digestion. I go by Runner's World Big Book of Marathon and HM Training. 600 calories approx 3 hours before a big run in simple carbs or 200 cals 1 hour before. As you are running, 100 cals 30 minutes into the run and 45 minutes thereafter.

    Why fuel up as you are running? As your body uses the anaerobic system (burning fuel without the presense of oxygen) you will be burning up your internal carb stores (glycogen). You have a limited supply. Different people have different levels and it depends how intense you run, but for most experienced runners, they should be able to run 15-20 miles and even beyond without worry of bonking (clearing out their glycogen supply). Running way beyond your aerobic threshold or poor training may cause you to bonk much sooner. The idea is to supplement the amount of glycogen you use up as you run but not replace it all together during the run. If you bonk too fast, then you are running faster than you should for your goal distance.

    If you run at a pace that is below your aerobic threshold (burning fuel in the presense of oxygen) then your fuel supply relies more on your internal fat storage as opposed to glycogen. Your body (in comparison to gycogen) has a virtual endless supply of fat to fuel long term activity.

    So this leads us into training and especially fasted training.

    If you have long steady training runs that you rely on your aerobic system, your body will begin to learn to rely more on fat burning as opposed to glycogen burning. Training fasted during these runs will slowly deplete your glycogen and will stimulate growth in this area. In other words, your body will soon learn to store more glycogen for future runs. As you sleep, your body begins to use up and lower your blood sugar. When your blood sugar goes below a certain point, it may either use fat or glycogen to fuel your bodies survival mechanisms as you sleep. If you train to rely on fat burning, your body will burn less glycogen but it will burn some glycogen none the less. So unless you eat something in the morning before you run, you will have diminished glycogen stores.

    This could be a good thing tho if you don't mind diminished performace in trade for stimulating growth.
    At a certain point, your body will experience diminished returns and poor performance will outweigh the benefits of stimulating the growth of glycogen storage. But in the beginning of the training season, the diminished supply of blood sugar and glycogen during fasted runs will take some getting used to as your body learns to power from your fat storage and aerobic system.

    If fasted running causes the body to learn to store more glycogen, it will become increasingly difficult to do fasted running, n'est-ce pas? ????

    I have actually read some conflicting physiology studies on this. Running (in general) especially in a fasted state burns more fat during exercise than other forms of exercise which up regulates production of fat mobilizing enzymes. This could be a good thing DURING your run; however, after the run the upregulation of these enzymes can make it easier for you to store fat. Whereas, stimulation of glycogen mobilizing enzymes would be best performed with anaerobic methods of training.

    The whole point of training, esp endurance running, is to train the body to optimally perform under certain specific conditions. Endurance training effects are meant to improve endurance performance--sometimes that does not coincide with other exercise goals such as weight loss or even overall health. Overall, the idea of doing fasted cardio for fat loss has been shown to be seriously flawed, if not outright debunked--but that's a different topic :smile:

    Glycogen sparing is obviously a good thing for endurance performance.

    Another point: a number of studies have shown that HIIT training can result in some of the same fat-burning adaptations as endurance training.This has lead to some people again trying to assert that HIIT training is a "one stop shop" that obviates the need for endurance training. However, every instinct of training and physiology says that you cannot train for a marathon by doing 20-min max interval training workouts, so I am looking forward to further research on this topic.

    I agree that HIIT wouldn't be appropriate for a competitive long distance runner to focus a majority of their time on. The SAID principle always applies to sports specific training.

    You're greatly underestimating the importance of enjoying the workout and the importance of being injury free. You'd be sacrificing one or both of these if you were doing HIIT as the majority of your workout.
  • jenilla1
    jenilla1 Posts: 11,118 Member
    I think it's an individual thing. I get sick and light-headed if I DON'T eat something before a run, but I couldn't run well on a full stomach, either. A banana or something light 20-30 minutes before works well for me. I drink a lot of water the night before, but only a little right before running, as too much water in my stomach makes me queasy, too. I don't need a lot of water while I run either (unless it's over 8-10 miles depending on the temp.) but I make sure I drink plenty throughout the day after my runs.
  • meerkat70
    meerkat70 Posts: 4,616 Member
    OK! Here is my skinny on fasted and unfasted running.

    First some fueling tips if you do decide to eat before running.

    Try different things. Different people react to different foods differently. You want to experiment in training runs so you know what works and doesn't work as you prepare for races. When you find something that works, you gonna want to replicate that before a race. This includes your day before pre-race meal.

    Eating too many calories before a run can lock up your stomach pretty bad and cause discomfort. As you run, blood is being diverted to the areas that require oxygen and liver glycogen and fat absorption during your run. This blood is diverted away from other functions such as digestion. I go by Runner's World Big Book of Marathon and HM Training. 600 calories approx 3 hours before a big run in simple carbs or 200 cals 1 hour before. As you are running, 100 cals 30 minutes into the run and 45 minutes thereafter.

    Why fuel up as you are running? As your body uses the anaerobic system (burning fuel without the presense of oxygen) you will be burning up your internal carb stores (glycogen). You have a limited supply. Different people have different levels and it depends how intense you run, but for most experienced runners, they should be able to run 15-20 miles and even beyond without worry of bonking (clearing out their glycogen supply). Running way beyond your aerobic threshold or poor training may cause you to bonk much sooner. The idea is to supplement the amount of glycogen you use up as you run but not replace it all together during the run. If you bonk too fast, then you are running faster than you should for your goal distance.

    If you run at a pace that is below your aerobic threshold (burning fuel in the presense of oxygen) then your fuel supply relies more on your internal fat storage as opposed to glycogen. Your body (in comparison to gycogen) has a virtual endless supply of fat to fuel long term activity.

    So this leads us into training and especially fasted training.

    If you have long steady training runs that you rely on your aerobic system, your body will begin to learn to rely more on fat burning as opposed to glycogen burning. Training fasted during these runs will slowly deplete your glycogen and will stimulate growth in this area. In other words, your body will soon learn to store more glycogen for future runs. As you sleep, your body begins to use up and lower your blood sugar. When your blood sugar goes below a certain point, it may either use fat or glycogen to fuel your bodies survival mechanisms as you sleep. If you train to rely on fat burning, your body will burn less glycogen but it will burn some glycogen none the less. So unless you eat something in the morning before you run, you will have diminished glycogen stores.

    This could be a good thing tho if you don't mind diminished performace in trade for stimulating growth.
    At a certain point, your body will experience diminished returns and poor performance will outweigh the benefits of stimulating the growth of glycogen storage. But in the beginning of the training season, the diminished supply of blood sugar and glycogen during fasted runs will take some getting used to as your body learns to power from your fat storage and aerobic system.

    If fasted running causes the body to learn to store more glycogen, it will become increasingly difficult to do fasted running, n'est-ce pas? ????

    I have actually read some conflicting physiology studies on this. Running (in general) especially in a fasted state burns more fat during exercise than other forms of exercise which up regulates production of fat mobilizing enzymes. This could be a good thing DURING your run; however, after the run the upregulation of these enzymes can make it easier for you to store fat. Whereas, stimulation of glycogen mobilizing enzymes would be best performed with anaerobic methods of training.

    The whole point of training, esp endurance running, is to train the body to optimally perform under certain specific conditions. Endurance training effects are meant to improve endurance performance--sometimes that does not coincide with other exercise goals such as weight loss or even overall health. Overall, the idea of doing fasted cardio for fat loss has been shown to be seriously flawed, if not outright debunked--but that's a different topic :smile:

    Glycogen sparing is obviously a good thing for endurance performance.

    Another point: a number of studies have shown that HIIT training can result in some of the same fat-burning adaptations as endurance training.This has lead to some people again trying to assert that HIIT training is a "one stop shop" that obviates the need for endurance training. However, every instinct of training and physiology says that you cannot train for a marathon by doing 20-min max interval training workouts, so I am looking forward to further research on this topic.

    I agree that HIIT wouldn't be appropriate for a competitive long distance runner to focus a majority of their time on. The SAID principle always applies to sports specific training.

    Dude! Do you even run?

    :)