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    IF beginner: 24 hours or 36 hours?

    Posts: 35 Member
    edited November 2024 in Health and Weight Loss
    Is it safe to fast more than 24 hours? I remember read it somewhere that it's not recommended to go over 24 hours for a beginner. But at the end of 24 hours period, I feel I could keep going for a bit longer - if there is any significant benefit to do that :)

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    • Posts: 1,917 Member
      what are you trying to accomplish? calorie deficit is what makes you lose weight so whether you fast for 24 or 36 hours - it is how much you eating during the eating times that will determine weight loss.
    • Posts: 8,578 Member
      And when you say 'fast' what exactly does that mean? And, as above, what are you trying to accomplish by fasting, if other than for religious purposes?

      There's no magic in when you eat or don't eat. Meal timing is irrelevant for weight management. :)
    • Posts: 16 Member
      What is IF?
    • Posts: 1,917 Member
      Holly2233 wrote: »
      What is IF?

      intermittent fasting
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    • Posts: 679 Member
      edited June 2017
      Give it a go. 36 hours isn't that much more than 24 hours if you've done that already. Obviously if you are working out during those fasting days, make sure to take it easier but I've tried a couple fasts for about that time and it was actually really mentally calming to be able to not eat and just relax with no food.

      Edit: I remember reading a study that showed that your metabolic rate did not decrease at all until the 36 hour mark where it began to slowly lower and returned to normal after refeeding.
    • Posts: 8,578 Member
      rdridi12 wrote: »
      Give it a go. 36 hours isn't that much more than 24 hours if you've done that already. Obviously if you are working out during those fasting days, make sure to take it easier but I've tried a couple fasts for about that time and it was actually really mentally calming to be able to not eat and just relax with no food.

      Edit: I remember reading a study that showed that your metabolic rate did not decrease at all until the 36 hour mark where it began to slowly lower and returned to normal after refeeding.

      The key, however, is what happens on the next non-fast day? It's very easy to overindulge after basically having starved yourself and completely undo any caloric deficit 'benefit' derived from the fast. :)
    • Posts: 932 Member
      snickerscharlie wrote: »

      There's no magic in when you eat or don't eat. Meal timing is irrelevant for weight management. :)

      Eh..it's the magic in my approach though. I eat non appetizing foods in pre-hungry time so the out of control hungry time would never come. That's how it is easy to create a deficit for me. Does the idea make sense to you? Non appetizing food, preemptive eating.

    • Posts: 35 Member
      rdridi12 wrote: »
      Give it a go. 36 hours isn't that much more than 24 hours if you've done that already. Obviously if you are working out during those fasting days, make sure to take it easier but I've tried a couple fasts for about that time and it was actually really mentally calming to be able to not eat and just relax with no food.

      Edit: I remember reading a study that showed that your metabolic rate did not decrease at all until the 36 hour mark where it began to slowly lower and returned to normal after refeeding.

      Thanks for the info on metabolic rate. I will probably try 36 hours next time, as long as it doesn't effect my sleep!
    • Posts: 679 Member
      snickerscharlie wrote: »
      show previous quotes

      The key, however, is what happens on the next non-fast day? It's very easy to overindulge after basically having starved yourself and completely undo any caloric deficit 'benefit' derived from the fast. :)


      For that reason I wouldn't really do the fast to save up calories. For me it was more of just having control of my emotions about eating and just giving me a little "cleanse" (I know everyone hates that) to be able to mentally get myself excited about cutting and sort of get rid of any cravings and things like that because I was concentrated on the fast.

      I do it for the mental benefit rather than the health benefits.
    • Posts: 932 Member
      snickerscharlie wrote: »
      show previous quotes

      I would never waste calories on non appetizing food, so... ;)

      And I would never waste mental and physical energy, time on constantly managing foods. ;)

      Actually when I have winded up enough deficit, I will eat like a king in other time so to speak.
    • Posts: 8,578 Member
      endlessfall16 wrote: »
      show previous quotes

      And I would never waste mental and physical energy, time on constantly managing foods. ;)

      Actually when I have winded up enough deficit, I will eat like a king in other time so to speak.

      To each their own. :)
    • Posts: 679 Member
      edited June 2017
      snickerscharlie wrote: »
      show previous quotes

      I would like to actually see this 'info.' Taking someone's word for it without seeing the science (if any) behind it just because it's what you'd like to hear is shortsighted and can be dangerous. :)


      Haha I agree, I actually just did a quick search to find something and found this. Actually says that metabolism speeds up around 36 hours and at 72 hours is at the same level as at 12 hours into the fast.


      https://www.ncbi.nlm.nih.gov/pubmed/8172872

      Edit: It also shows that at 12 hours they were burning about 66% of calories from fat, at 36 hours they were burning about 80% calories from fat and at 72 hours it was about 93% calories from fat.
    • Posts: 35 Member
      rdridi12 wrote: »
      show previous quotes


      Haha I agree, I actually just did a quick search to find something and found this. Actually says that metabolism speeds up around 36 hours and at 72 hours is at the same level as at 12 hours into the fast.


      https://www.ncbi.nlm.nih.gov/pubmed/8172872

      Edit: It also shows that at 12 hours they were burning about 66% of calories from fat, at 36 hours they were burning about 80% calories from fat and at 72 hours it was about 93% calories from fat.

      Interesting! I will probably try a 3-4 days fast after Christmas season.
    • Posts: 679 Member
      julie20170512 wrote: »
      show previous quotes

      Interesting! I will probably try a 3-4 days fast after Christmas season.


      I would advise against that without checking with your doctor.
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    • Posts: 35 Member
      snickerscharlie wrote: »
      And when you say 'fast' what exactly does that mean? And, as above, what are you trying to accomplish by fasting, if other than for religious purposes?

      There's no magic in when you eat or don't eat. Meal timing is irrelevant for weight management. :)

      For me, IF is a very effective method to manage my food intakes. I fast one day a week, and the rest of week I eat 1200cal + all exercise cals, no struggle with food cravings.
    • Posts: 8,578 Member
      edited June 2017
      julie20170512 wrote: »
      show previous quotes

      For me, IF is a very effective method to manage my food intakes. I fast one day a week, and the rest of week I eat 1200cal + all exercise cals, no struggle with food cravings.

      How tall are you, what is your current weight as well as your goal weight? What do you have your rate of loss per week set at?

      Edited to add: Also, how long have you been doing this weekly fasting cycle for?

    • Posts: 35 Member
      OMG is this the new trend? To see how long you can go without eating. This is not IF.[/quote]

      :D It will be a yearly cleanse kinda thing, if my body is ok to do that. Right now I will stick to my one day per week fasting plan, since I am still new at this.
    • Posts: 8,578 Member
      edited June 2017
      julie20170512 wrote: »
      :D It will be a yearly cleanse kinda thing, if my body is ok to do that. Right now I will stick to my one day per week fasting plan, since I am still new at this.

      What do you think you will 'cleanse' yourself of?

      And don't get me wrong, I'm a fan of IF, and I've been doing it for years - long before it had a fancy-schmantsy name. ;)
    • Posts: 35 Member
      snickerscharlie wrote: »
      show previous quotes

      What do you think you will 'cleanse' yourself of?

      And don't get me wrong, I'm a fan of IF, and I've been doing it for years - long before it had a fancy-schmantsy name. ;)

      Guess It's like a full reboot of the body. What kind of IF you have been practicing? :)
    • Posts: 16,011 Member
      1. Cleanses are not a thing. Your liver and kidneys do that for you every day.
      2. Maybe I'm out of the loop, but this doesn't sound like IF to me. I thought IF was either eating within a short window every day, or having one or two very-low cal days per week, while eating close to or at maintenance the other days. Do you know what your maintenance calories are? That sounds like not enough food overall, unless you are very small.
    • Posts: 6,771 Member
      OP what are your current stats? The type of fasting you are employing, particularly combined with eating very low on the other days is in no way how intermittent fasting is supposed to be practiced. You are creating an incredibly large deficit, even if you're petite.
    • Posts: 35 Member
      kimny72 wrote: »
      1. Cleanses are not a thing. Your liver and kidneys do that for you every day.
      2. Maybe I'm out of the loop, but this doesn't sound like IF to me. I thought IF was either eating within a short window every day, or having one or two very-low cal days per week, while eating close to or at maintenance the other days. Do you know what your maintenance calories are? That sounds like not enough food overall, unless you are very small.

      That's sound like exactly what I am doing - having one zero cals day per week, the rest at maintenance rate (based on MFP). Why this is not IF? I am confused now.

      I am only 5"1 with a very small frame though :p
    • Posts: 8,578 Member
      julie20170512 wrote: »
      show previous quotes

      That's sound like exactly what I am doing - having one zero cals day per week, the rest at maintenance rate (based on MFP). Why this is not IF? I am confused now.

      I am only 5"1 with a very small frame though :p

      What is your current weight and goal weight, though?
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