How much fat can I lose if I fast for a whole day?

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Replies

  • toxikon
    toxikon Posts: 2,383 Member
    I'll be honest here, I find it funny that so many CICO proponents are saying you'll only lose water weight if you don't eat anything for a day.

    So... somehow fasting negates the effects of CICO? Wat?

    A pound of fat weighs about 3500 calories. OP's TDEE calories are 3300 calories. That means, according to the science of CICO, OP could lose just under 1lbs of fat in a day of water fasting.

    One day of water fasting is not harmful unless OP has some sort of medical condition that makes it so. I've fasted 48 hours for medical procedures and my doctor never seemed concerned about that.

    The main question here is: will that 1lbs of fat stay off? Will OP be so ravenous in the days following the fast that he overeats and negates that 1lbs loss? That's the one thing I'd urge OP to consider.
  • tinkerbellang83
    tinkerbellang83 Posts: 9,142 Member
    edited February 2018
    toxikon wrote: »
    I'll be honest here, I find it funny that so many CICO proponents are saying you'll only lose water weight if you don't eat anything for a day.

    So... somehow fasting negates the effects of CICO? Wat?

    A pound of fat weighs about 3500 calories. OP's TDEE calories are 3300 calories. That means, according to the science of CICO, OP could lose just under 1lbs of fat in a day of water fasting.

    One day of water fasting is not harmful unless OP has some sort of medical condition that makes it so. I've fasted 48 hours for medical procedures and my doctor never seemed concerned about that.

    The main question here is: will that 1lbs of fat stay off? Will OP be so ravenous in the days following the fast that he overeats and negates that 1lbs loss? That's the one thing I'd urge OP to consider.

    I think the issue here is a lot of assumptions are being made, the OP asked about fasting for one whole day, not fasting one day every week - we all know weight loss isn't linear so the fact is they may lose just under a pound, they may not, if they don't make any other changes and does this as a one off they may just see the water weight come off and then go straight back on, which achieves sweet FA
  • amtyrell
    amtyrell Posts: 1,447 Member
    1 day is about 1/29000 th of your life . 1 day doesn't matter compared to the other 28999 days.
  • Tacklewasher
    Tacklewasher Posts: 7,122 Member
    toxikon wrote: »
    I'll be honest here, I find it funny that so many CICO proponents are saying you'll only lose water weight if you don't eat anything for a day.

    So... somehow fasting negates the effects of CICO? Wat?

    A pound of fat weighs about 3500 calories. OP's TDEE calories are 3300 calories. That means, according to the science of CICO, OP could lose just under 1lbs of fat in a day of water fasting.

    One day of water fasting is not harmful unless OP has some sort of medical condition that makes it so. I've fasted 48 hours for medical procedures and my doctor never seemed concerned about that.

    The main question here is: will that 1lbs of fat stay off? Will OP be so ravenous in the days following the fast that he overeats and negates that 1lbs loss? That's the one thing I'd urge OP to consider.

    Only nitpick I have is it may not be just fat that is lost. It could be lean tissue as well. So the actual fat loss may be less than the 3300/3500. No idea what the split actually would be, but I doubt it would all be fat.

    But, in general, I agree with you.
  • heybales
    heybales Posts: 18,842 Member
    edited February 2018
    To only answer your question.

    If your TDEE is really about 3300,
    and you really kept just as active as that on a fasting day,
    and you did not eat more than normal day before or after -

    You would lose about 1 lb of fat over the course of 2 days.

    First day would be mainly fat as that is what your body is mainly burning anyway, outside of post meal elevated insulin induced carb burn of what you ate.
    You'll also use most of the carbs from your liver with attached water, and if any exercise or intense/long enough to require carbs from muscles, some use and loss of water weight there too.

    Day one should be a bigger than 1 lb drop, much being water, and waste from prior day eating of course.

    Second day when you first eat, your carbs eaten are going to go to refill the liver and muscles, so increased water weight there.
    That will take you out of elevated-insulin mode really quick and back to fat burning mode sooner than normal after eating (that's how deficit for fat loss works anyway, just smaller scale)

    Day two would be increased fat burning too then, but stomach filled back up. Would still lose some fat weight.

    So over the course of 2 days - yes to almost 1 lb of fat.

    If all else remained the same.
  • kimny72
    kimny72 Posts: 16,011 Member
    edited February 2018
    tinkerbellang83 wrote: »
    toxikon wrote: »
    I'll be honest here, I find it funny that so many CICO proponents are saying you'll only lose water weight if you don't eat anything for a day.

    So... somehow fasting negates the effects of CICO? Wat?

    A pound of fat weighs about 3500 calories. OP's TDEE calories are 3300 calories. That means, according to the science of CICO, OP could lose just under 1lbs of fat in a day of water fasting.

    One day of water fasting is not harmful unless OP has some sort of medical condition that makes it so. I've fasted 48 hours for medical procedures and my doctor never seemed concerned about that.

    The main question here is: will that 1lbs of fat stay off? Will OP be so ravenous in the days following the fast that he overeats and negates that 1lbs loss? That's the one thing I'd urge OP to consider.

    I think the issue here is a lot of assumptions are being made, the OP asked about fasting for one whole day, not fasting one day every week - we all know weight loss isn't linear so the fact is they may lose just under a pound, they may not, if they don't make any other changes and does this as a one off they may just see the water weight come off and then go straight back on, which achieves sweet FA

    ^ This. The way the question was asked did not suggest a plan, it sounded more like "How long would I have to not eat to see the scale move" Which is concerning. It didn't sound to me like he was considering a plan to fast 1 day a week to make his goal easier to hit for the week, but how far he can push himself in order to lose weight. At 300 lbs, I don't think it's going out on a limb to suggest that he should first get a consistent, well thought out plan in place before jumping into - how much instant gratification can I get from not eating as long as I can take it?

    If we're misreading he can come back and correct us. Some people do quite well working fasting into there routine, I just didn't think that's what it sounded like was happening.
  • lemurcat12
    lemurcat12 Posts: 30,886 Member
    Focusing on how much weight you lose in a day is a bad focus.

    The question is what your calorie deficit for the week would be (assuming you keep that up consistently). Without that information we can't tell you. At your weight aiming for 2-3 lb/week would probably be fine.
  • cwolfman13
    cwolfman13 Posts: 41,865 Member
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  • pinuplove
    pinuplove Posts: 12,871 Member
    PAV8888 wrote: »
    A 29X lb person contemplating fasts for weight control has other more approachable, more likely to lead to success, less likely to lead to problem behavior, all around much better and simpler to implement and continue to implement tools available to them.

    In other words this avenue of exploration is quite likely the wrong rabbit hole for them!

    Now it's perfectly okay to argue, if that's what you want, that alternate-day fasting or other intermittent fasting protocols will provide the best cost-benefit to somebody just starting their weight loss endeavor from the just under 300 lb point.

    I just think that you would be in error to do so :smile:

    Thank you for saying what I was thinking but couldn't formulate into a coherent post :smile:
  • jennifer_417
    jennifer_417 Posts: 12,344 Member
    Need2Exerc1se wrote: »
    jennifer_417 wrote: »
    I have no idea, but I find this question slightly concerning. I'd look into some healthier weight loss options.

    There is nothing unhealthy about a one day fast.

    I agree. It's the mindset behind it that I find concerning.
  • nowine4me
    nowine4me Posts: 3,985 Member
    Zero
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