Fasted cardio

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mooshca7
mooshca7 Posts: 9 Member
in Fitness and Exercise
Does anyone know if working out after eating is as effective as fasted cardio?

I'm doing 20:4 intermittent fasting but can't figure out where to fit in exercise. Anyone have any recommendations?
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  • sijomial
    sijomial Posts: 19,811 Member
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    Assuming you are talking about exercise performance when you say "effective"....

    For some people fasted exercise is more effective.
    For some less effective.
    For some an irrelevance.

    I'm mostly in the irrelevance camp, longest cycle ride this year unfed was 40 miles and felt just the same as 40 miles when fed but I had just returned from an all inclusive holiday which is a very effective form of carb loading!

    For most cardio up to a couple of hours I can perform the same fasted, just eaten, eating while riding, eaten a few hours ago.

    There's a limit on how long you can go unfed though but that's not a big concern to people who don't do endurance cardio. For more typical exercise durations you have plenty of fuel onboard and don't need (as opposed to want) to fuel from food just eaten.
  • NorthCascades
    NorthCascades Posts: 10,970 Member
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    How much fat (vs carb) you burn while exercising isn't important for weight loss. Only the calories you burn matter. Easy and exercise when it's convenient for you, this is a tortoise and the hare kind of thing.
  • BrianSharpe
    BrianSharpe Posts: 9,248 Member
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    What do you mean by "effective"? If you're thinking in term of fat loss a number of studies have determined that the difference is so small as to be immaterial. If you're speaking about having enough energy to complete your workout that becomes more individual. Most people eating a reasonably well balanced diet will have enough stored glycogen to perform 90 to 120 minutes of moderate exercise. Typically I will run or bike fasted up to 90 or so, If I'm going longer I'll eat something light an hour or so before working out as I don't like running or biking on a full stomach (but that too is highly individual).
  • jhanleybrown
    jhanleybrown Posts: 240 Member
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    Everyone here is focused on weight loss...but there are apparently other benefits in doing this...there are studies out there by serious science centers that are showing exercising on an empty stomach/fasted:

    1) may have a large positive impact on improving body's ability to regulate insulin
    2) may have a large and positive impact on the body's cells cleaning up waste including waste protein removal (one of the causes of Alzheimers)

    But it doesn't help you lose weight faster.
  • AnnPT77
    AnnPT77 Posts: 32,198 Member
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    Effect on weight loss is trivial to nonexistent. Effect on exercise performance/intensity is individual.

    My workouts are arduous if I try to do them fasted, so I don't. If I eat before working out, one of two things happens: I can work at a higher intensity, and get through a distance based workout a little sooner (while feeling less awful); I can work at the lower intensity for a longer time period (without feeling awful) thus burning a few more calories.

    This may or may not be true for you. Try it a few times (once is not definitive) and see. What's the worst that could happen?

    Usually, working out at a time that's convenient for us personally, in a state that's relatively more enjoyable, will result in working out more regularly, and workouts we actually do will of course burn more calories that workouts we skip because they're inconvenient or miserable. ;)
  • lorrpb
    lorrpb Posts: 11,464 Member
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    Fit in your exercise wherever it works best in your schedule based on the rest of your commitments. That's most effective for consistency and consistency is most effective for both fitness and weight loss.
    As an aside, IF has no benefit for weight loss in and of itself. It only matters if it helps you to manage your calories better, which is purely a personal thing.
  • NorthCascades
    NorthCascades Posts: 10,970 Member
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    jhanleybrown wrote: »
    Everyone here is focused on weight loss...but there are apparently other benefits in doing this...there are studies out there by serious science centers that are showing exercising on an empty stomach/fasted:

    1) may have a large positive impact on improving body's ability to regulate insulin
    2) may have a large and positive impact on the body's cells cleaning up waste including waste protein removal (one of the causes of Alzheimers)

    But it doesn't help you lose weight faster.

    For what it's worth, exercise improves sensitivity to insulin. So if you need to eat before you do yours, you're still sounds a good thing for yourself in this regard.
  • seanrodg
    seanrodg Posts: 4 Member
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    mooshca7 wrote: »
    Does anyone know if working out after eating is as effective as fasted cardio?

    I'm doing 20:4 intermittent fasting but can't figure out where to fit in exercise. Anyone have any recommendations?

    That’s great you’re asking questions and trying different approaches. It’s the best way to find the fit your body will respond to.

    I do intermittent fasting as well and also run, bike and do HIIT all fasted about 30 - 45 minutes after waking up. My body responds well and I’ve found that my desire for sugar/carbs is reduced and I use good fats and protein with high fiber carbohydrates to refuel. Oatmeal, butter, Greek yogurt, walnuts, blueberries, eggs etc.

    The science behind fasted cardio is always based on studies of adults who may not have had any experience with fasted cardio. I don’t think the studies are conclusive as our bodies adapt to this fasted state by storing more glycogen in the liver and muscles. I’ve run 2.5 hours without nutrition and felt fine afterwards. The secret was my heart rate was in the sweet spot of 130 which was my target rate for my age. (180 - age).

    Read some Dr. Phil Mafetone for some great insight into his approach on fueling, exercise and good clean living.
    https://philmaffetone.com/

    Be well!
  • BoxerBrawler
    BoxerBrawler Posts: 2,032 Member
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    For me, working out fasted always means more energy, stamina, focus and strength vs. if I eat first I feel like taking a nap lol! Also I don't like to eat first because each day my workouts are different so I'll never know what I'll need to re-fuel until after I've done it :smile:
  • seanrodg
    seanrodg Posts: 4 Member
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    mmapags wrote: »
    jhanleybrown wrote: »
    Everyone here is focused on weight loss...but there are apparently other benefits in doing this...there are studies out there by serious science centers that are showing exercising on an empty stomach/fasted:

    1) may have a large positive impact on improving body's ability to regulate insulin
    2) may have a large and positive impact on the body's cells cleaning up waste including waste protein removal (one of the causes of Alzheimers)

    But it doesn't help you lose weight faster.

    Please post these studies.

    Plenty to read here:

    https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/effects-of-aerobic-exercise-performed-in-fasted-v-fed-state-on-fat-and-carbohydrate-metabolism-in-adults-a-systematic-review-and-metaanalysis/0EA2328A0FF91703C95FD39A38716811

    https://www.tandfonline.com/doi/abs/10.1080/0264041031000140527

    https://annals.org/aim/article-abstract/693343/direct-binding-studies-adrenergic-receptors-biochemical-physiologic-clinical-implications

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2142449/

    https://link.springer.com/article/10.1007/s00125-012-2676-0

  • mooshca7
    mooshca7 Posts: 9 Member
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    Really great feedback. Thank you for all your insight and recommendations. I love how everyone is so willing to offer their help and support to complete strangers. Thanks again
  • jhanleybrown
    jhanleybrown Posts: 240 Member
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    seanrodg wrote: »
    mmapags wrote: »
    jhanleybrown wrote: »
    Everyone here is focused on weight loss...but there are apparently other benefits in doing this...there are studies out there by serious science centers that are showing exercising on an empty stomach/fasted:

    1) may have a large positive impact on improving body's ability to regulate insulin
    2) may have a large and positive impact on the body's cells cleaning up waste including waste protein removal (one of the causes of Alzheimers)

    But it doesn't help you lose weight faster.

    Please post these studies.

    Plenty to read here:

    https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/effects-of-aerobic-exercise-performed-in-fasted-v-fed-state-on-fat-and-carbohydrate-metabolism-in-adults-a-systematic-review-and-metaanalysis/0EA2328A0FF91703C95FD39A38716811

    https://www.tandfonline.com/doi/abs/10.1080/0264041031000140527

    https://annals.org/aim/article-abstract/693343/direct-binding-studies-adrenergic-receptors-biochemical-physiologic-clinical-implications

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2142449/

    https://link.springer.com/article/10.1007/s00125-012-2676-0

    Here's one on junk protein removal:
    https://news.harvard.edu/gazette/story/2019/02/exercise-fasting-shown-to-help-cells-shed-defective-proteins/
  • janejellyroll
    janejellyroll Posts: 25,763 Member
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    jhanleybrown wrote: »
    seanrodg wrote: »
    mmapags wrote: »
    jhanleybrown wrote: »
    Everyone here is focused on weight loss...but there are apparently other benefits in doing this...there are studies out there by serious science centers that are showing exercising on an empty stomach/fasted:

    1) may have a large positive impact on improving body's ability to regulate insulin
    2) may have a large and positive impact on the body's cells cleaning up waste including waste protein removal (one of the causes of Alzheimers)

    But it doesn't help you lose weight faster.

    Please post these studies.

    Plenty to read here:

    https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/effects-of-aerobic-exercise-performed-in-fasted-v-fed-state-on-fat-and-carbohydrate-metabolism-in-adults-a-systematic-review-and-metaanalysis/0EA2328A0FF91703C95FD39A38716811

    https://www.tandfonline.com/doi/abs/10.1080/0264041031000140527

    https://annals.org/aim/article-abstract/693343/direct-binding-studies-adrenergic-receptors-biochemical-physiologic-clinical-implications

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2142449/

    https://link.springer.com/article/10.1007/s00125-012-2676-0

    Here's one on junk protein removal:
    https://news.harvard.edu/gazette/story/2019/02/exercise-fasting-shown-to-help-cells-shed-defective-proteins/

    That study isn't on humans.
  • MelanieCN77
    MelanieCN77 Posts: 4,047 Member
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    I can do fasted if it's very VERY soon after I wake up, but not otherwise. It's almost like getting the thing done before I'm fully present for the day works, but after even an hour or so it just feels like a huge drag and is not enjoyable. So get up and go, or breakfast.
  • helen_goldthorpe
    helen_goldthorpe Posts: 340 Member
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    I have always done a fair amount of training fasted because it often works for me to exercise in the morning, but I don't have enough time to digest food properly before exercising so I tend to work out then eat then go to work. It's more about time management than expecting major benefits from it. But I do tend to do harder sessions that I'll need fuel for in the evenings so I mix and match depending on the workouts and my other plans.
  • Azdak
    Azdak Posts: 8,281 Member
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    I had a more detailed response, but accidentally hit a button and erased it. Not sure I have the interest to rewrite it.

    Suffice to say that the Harvard Gazette article talked about fasting and it talked about exercise, but it never mentioned fasted cardio as something they were looking at (unless I misread it).

    While you have to start somewhere, and micro level studies are the obvious starting point, it’s a long, long, long way from seeing some isolated activity at the molecular level to being able to make specific lifestyle recommendations. So right now (and obviously this could change with more science), I don’t see anything to support claims of any specific health benefits for fasted cardio.

    Here is still my go to study on the effects of increased fat oxidation during exercise:

    https://www.ncbi.nlm.nih.gov/pubmed/19305201

    IMO, if you haven’t read this (and I would say even most fitness professionals haven’t), then I don’t think you can really discuss the topic.


  • seanrodg
    seanrodg Posts: 4 Member
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    Mmapags was asking for the studies (read entire thread). I was not posting them to support the claims.
    They were posted by another member. I just jumped in at the wrong place. Sorry for the confusion. But thanks for the study you posted. Awesome reading. Fat oxidation! When I ran Ultras I definitely trained 2 - 7 hours at a time and I always started fasted at an easy pace for the first 2+ hours. I wanted to stay in the “fat burning” zone as long as possible to stave off having to take on nutrition (carbohydrates). I use heart rate training and used to use it as well as part of my race strategy. The data suggests that HR (or VO2 max) does play a role in fat oxidation.

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