IF beginner: 24 hours or 36 hours?

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  • rileysowner
    rileysowner Posts: 8,160 Member
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    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!

    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. :)

    Read the ebook "Eat, Stop, Eat" or a whole host of other things on it. There is nothing dangerous about a healthy person fasting from calories for 24 hours (or 36 for that matter). Brad Pilon has done the research and does actually cite the studies. Fasting has been extensively studied.
  • Rammer123
    Rammer123 Posts: 679 Member
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    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.

    If I recall correctly, metabolic rate doesn't slow until about 72 hours, but it would generally not be advisable to fast that long as it would be very demanding on one's body and create a much higher likelihood of having a binge that will destroy any deficit you might have established.


    Yeah I posted the link to the study a couple posts after.

    Also showed the percentage of fat calories burned increased from roughly 66% to 80% and 93% at hours 12, 36 and 72.
  • kimny72
    kimny72 Posts: 16,013 Member
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    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

    What is your current weight and goal weight, though?

    5'1, 123lb. I am eating avg 1600 cals per day when I am not fasting, and has been losing around 0.5 to 1lb/wk since I started.

    I personally can't do 16:8 everyday, I am a hopeless snacker

    Thanks for clarifying :). Sorry if it sounds like we're picking! I would just say please consider not doing the 4 day fast you mentioned, if your reasons are mostly "cleansing". It won't do that, and if you are capable of fasting 24-36 hours without rebounding into eating everything that moves the next day (which I would LOL!) it sounds like you have plenty of control already.
  • snickerscharlie
    snickerscharlie Posts: 8,578 Member
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    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

    What is your current weight and goal weight, though?

    5'1, 123lb. I am eating avg 1600 cals per day when I am not fasting, and has been losing around 0.5 to 1lb/wk since I started.

    I personally can't do 16:8 everyday, I am a hopeless snacker

    Upthread you said you were only eating 1200 calories per day:
    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.

    That's a big difference. Which is it?
  • rileysowner
    rileysowner Posts: 8,160 Member
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    For those reading this that think starvation for a day is intermittent fasting normally IF is banded about as either chosen a period of time to eat ie eat in the 8 hours and fast for 16 or have days where you eat at a lower calorie 500-600 for a couple of days then the rest of the week at around maintainance but you would have some food.

    Not eating for 36 hours is fasting and not the typical IF people would do.

    No, it is not. That is but one form of Intermittent Fasting popularized by Martin Burkan. It is not the only one, and might not even be the original one. Brad Pilon author of Eat Stop Eat may have been first. Either way, not consuming calories for 24 hours 1 or 2 times a week is intermittent fasting.
  • Rammer123
    Rammer123 Posts: 679 Member
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    I wouldn't call that intermittent fasting.

    It is. Intermittent fasting can be either every day extending ones overnight fast and establishing one's deficit through eating at a calorie deficit during the smaller eating window one has each day. The other method is fasting once or twice a week from all food, and eating an maintenance on the other days. This sort of Intermittent Fasting establishes one's deficit by the fast time. Usually those fasts are 24 hours, but assuming the OP is healthy, 36 hours once a week and eating at maintenance the other days would be fine.

    IF or 5:2 as you're describing has two very low calorie days, not food free days. That creates the deficit. If someone has maintenance of say 2000 calories, they would be creating a 4000 calorie per week deficit. If their maintenance is 2000 calories that is very likely too big a deficit.


    Whats the difference between that and a person who has a 2500 calorie maintenance and eats two very low calorie days at 500 calories each day? They still end in a 4,000 calorie deficit for the week. Smaller percentage of the maintenance but not by much.
  • TR0berts
    TR0berts Posts: 7,739 Member
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    I wouldn't call that intermittent fasting.

    It is. Intermittent fasting can be either every day extending ones overnight fast and establishing one's deficit through eating at a calorie deficit during the smaller eating window one has each day. The other method is fasting once or twice a week from all food, and eating an maintenance on the other days. This sort of Intermittent Fasting establishes one's deficit by the fast time. Usually those fasts are 24 hours, but assuming the OP is healthy, 36 hours once a week and eating at maintenance the other days would be fine.

    IF or 5:2 as you're describing has two very low calorie days, not food free days. That creates the deficit. If someone has maintenance of say 2000 calories, they would be creating a 4000 calorie per week deficit. If their maintenance is 2000 calories that is very likely too big a deficit.

    That's just over 1 lb (~1.14 lb) per week, so it's not necessarily too big. And there are other IF protocols other than 16:8 or 5:2 that have prescribed zero Calorie days.

    As far as 36 hrs goes, that seems fairly normal for a day of fasting - stop eating ~6PM, fast the next day, start eating again ~6AM the following. Or whatever time(s) you stop/start eating.
  • rileysowner
    rileysowner Posts: 8,160 Member
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    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.

    I find it very difficult to imagine, even at 5'1" your maintenance is 1200 calories. That is generally considered the minimum for women to get their nutritional needs (note MINIMUM not MAINTENANCE). Unless you are far older than you look, or extremely limited in your mobility like in a wheelchair or always using a walker, your maintenance is probably more than that. If you exercise at all that will increase your maintenance.
  • Rammer123
    Rammer123 Posts: 679 Member
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    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.

    I find it very difficult to imagine, even at 5'1" your maintenance is 1200 calories. That is generally considered the minimum for women to get their nutritional needs (note MINIMUM not MAINTENANCE). Unless you are far older than you look, or extremely limited in your mobility like in a wheelchair or always using a walker, your maintenance is probably more than that. If you exercise at all that will increase your maintenance.


    She said she's losing 0.5-1 pound per week.
  • julie20170512
    julie20170512 Posts: 35 Member
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    kimny72 wrote: »
    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

    What is your current weight and goal weight, though?

    5'1, 123lb. I am eating avg 1600 cals per day when I am not fasting, and has been losing around 0.5 to 1lb/wk since I started.

    I personally can't do 16:8 everyday, I am a hopeless snacker

    Thanks for clarifying :). Sorry if it sounds like we're picking! I would just say please consider not doing the 4 day fast you mentioned, if your reasons are mostly "cleansing". It won't do that, and if you are capable of fasting 24-36 hours without rebounding into eating everything that moves the next day (which I would LOL!) it sounds like you have plenty of control already.

    Overeating after fast was also my challenge at the beginning, now I am trying to break the fast at around 9ish, no much time left for binge eating before bed :smiley: so it is pretty much under control now
  • julie20170512
    julie20170512 Posts: 35 Member
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    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

    What is your current weight and goal weight, though?

    5'1, 123lb. I am eating avg 1600 cals per day when I am not fasting, and has been losing around 0.5 to 1lb/wk since I started.

    I personally can't do 16:8 everyday, I am a hopeless snacker

    Upthread you said you were only eating 1200 calories per day:
    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.

    That's a big difference. Which is it?

    I didnt said 1200 cal, it's 1200 plus exercise cals, depending on my activity level. My avg is 1600 cals per day
  • TR0berts
    TR0berts Posts: 7,739 Member
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    rdridi12 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.

    I find it very difficult to imagine, even at 5'1" your maintenance is 1200 calories. That is generally considered the minimum for women to get their nutritional needs (note MINIMUM not MAINTENANCE). Unless you are far older than you look, or extremely limited in your mobility like in a wheelchair or always using a walker, your maintenance is probably more than that. If you exercise at all that will increase your maintenance.


    She said she's losing 0.5-1 pound per week.

    Since she said she's fasting one day per week, that would indicate that her maintenance is somewhere between 1750-3500 Cals per day. So, as that poster you quoted said, OP's maintenance clearly isn't 1200 Cals per day, which would result in ~0.3 lb per week.
  • Rammer123
    Rammer123 Posts: 679 Member
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    TR0berts wrote: »
    rdridi12 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.

    I find it very difficult to imagine, even at 5'1" your maintenance is 1200 calories. That is generally considered the minimum for women to get their nutritional needs (note MINIMUM not MAINTENANCE). Unless you are far older than you look, or extremely limited in your mobility like in a wheelchair or always using a walker, your maintenance is probably more than that. If you exercise at all that will increase your maintenance.


    She said she's losing 0.5-1 pound per week.

    Since she said she's fasting one day per week, that would indicate that her maintenance is somewhere between 1750-3500 Cals per day. So, as that poster you quoted said, OP's maintenance clearly isn't 1200 Cals per day, which would result in ~0.3 lb per week.


    I never said that was her maintenance?
  • snickerscharlie
    snickerscharlie Posts: 8,578 Member
    edited June 2017
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    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

    What is your current weight and goal weight, though?

    5'1, 123lb. I am eating avg 1600 cals per day when I am not fasting, and has been losing around 0.5 to 1lb/wk since I started.

    I personally can't do 16:8 everyday, I am a hopeless snacker

    Upthread you said you were only eating 1200 calories per day:
    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.

    That's a big difference. Which is it?

    I didnt said 1200 cal, it's 1200 plus exercise cals, depending on my activity level. My avg is 1600 cals per day

    But the exercise in and of itself depletes your fuel reserves and you need to eat back the calories expended just to break even.

    What I mean is, if you eat 1200 calories per day, then 'earn' 400 additional calories via exercise (because your body burned those 400 calories performing the exercise in the first place) and then eat those 400 back, you're still only replenishing at a rate of 1200 calories per day, not 1600.

    Edited to add: And if you're fasting for one day out of seven, that means your average daily intake is just over a 1000 calories per day.
  • rybo
    rybo Posts: 5,424 Member
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    IF is the new crossfit, lots and lots of haters who have never tried it.
    Lots of people who want to try it because they think it works miracles.
    Lots of people badly informed about what all it entails.

    Oh and here's a shocking little tidbit for some... certain IF protocols can be followed by people who are maintaining or even looking to gain weight.
  • snickerscharlie
    snickerscharlie Posts: 8,578 Member
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    rybo wrote: »
    Oh and here's a shocking little tidbit for some... certain IF protocols can be followed by people who are maintaining or even looking to gain weight.

    Yup. Lost the weight I needed to using IF.

    Been in maintenance for almost two years using IF, too.

    Bottom line is IF is just another way that works for some people to control their weight management goals - whatever those goals may be. :)