Why is the first week's weight loss usually so big?

Orphia
Orphia Posts: 7,097 Member
edited November 19 in Health and Weight Loss
Why is the first week's weight loss usually so big?

I've seen people say it's water weight. If so, why does the body lose so much water when you start eating at a deficit?

(Just something that's puzzled me when on my walks recently. :) )

Replies

  • ncboiler89
    ncboiler89 Posts: 2,408 Member
    You lose a *kitten* ton of water.
  • malibu927
    malibu927 Posts: 17,562 Member
    Less sodium and/or carbs, usually
  • bpetrosky
    bpetrosky Posts: 3,911 Member
    My understanding is that being on a calorie deficit causes the body to use glycogen stores more, which releases water that's bound up in those molecules.
  • Orphia
    Orphia Posts: 7,097 Member
    bpetrosky wrote: »
    My understanding is that being on a calorie deficit causes the body to use glycogen stores more, which releases water that's bound up in those molecules.

    Thanks. That gives me a glimmer of understanding from my limited knowledge of cell behaviour.
  • bpetrosky
    bpetrosky Posts: 3,911 Member
    If I recall correctly, 1g of glycogen binds 3g of water.

    I've read different takes on it where the low carb/keto people say you only use glycogen when your very low on carbs, and I've heard it said you use glycogen whenever you're in deficit. I don't know which would be more true, honestly.
  • Liftng4Lis
    Liftng4Lis Posts: 15,151 Member
    bpetrosky wrote: »
    My understanding is that being on a calorie deficit causes the body to use glycogen stores more, which releases water that's bound up in those molecules.

    Yep
  • BWBTrish
    BWBTrish Posts: 2,817 Member
    in my case... my body hold on to a lot of water...in my feet and hands. And i mean a lot!!!
    totally blown up.

    i lost that all in the first month or rather week by going salt less
    32 pounds in total
  • MsBonfire
    MsBonfire Posts: 12 Member
    I read somewhere that fat cells hold a lot of water. When they start to shrink they release the water or something like that.
  • echmainfit619
    echmainfit619 Posts: 333 Member
    It's also why losing the first 10 pounds can be a lot easier than the last 10.
  • karahm78
    karahm78 Posts: 505 Member
    Also typically the first week you start a diet you start consuming less, so there is less "volume" going through your system (and therefore less weight).
  • Sued0nim
    Sued0nim Posts: 17,456 Member
    edited June 2015
    When you restrict calories you have
    1) less waste in your system
    2) generally reduce carbs which reduce water weight by stripping the glycogen stores in your liver and muscles ...each gramme of glycogen binds to something like 3 grammes of water
    3) generally reduce sodium ...again with the water

    Eat a "normal" diet for a day and it will come back
  • Orphia
    Orphia Posts: 7,097 Member
    Thanks, all, for the replies.
    rabbitjb wrote: »
    When you restrict calories you have
    1) less waste in your system
    2) generally reduce carbs which reduce water weight by stripping the glycogen stores in your liver and muscles ...each gramme of glycogen binds to something like 3 grammes of water
    3) generally reduce sodium ...again with the water

    Eat a "normal" diet for a day and it will come back

    Very helpful!
  • TimothyFish
    TimothyFish Posts: 4,925 Member
    While part of it may be "water weight", I've always suspected that the quick weight loss during the first week has more to do with the amount of food in your gut. Your body can only process so much food at a time, so when we overeat, it all gets backed up and we keep stuffing more food on top of it. When we eat the proper amounts, the body is able to process the food at the same rate that we add it to the system, so we end up carrying less food around.
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  • EvgeniZyntx
    EvgeniZyntx Posts: 24,208 Member
    TimothyFish wrote: »
    While part of it may be "water weight", I've always suspected that the quick weight loss during the first week has more to do with the amount of food in your gut. Your body can only process so much food at a time, so when we overeat, it all gets backed up and we keep stuffing more food on top of it. When we eat the proper amounts, the body is able to process the food at the same rate that we add it to the system, so we end up carrying less food around.

    It's both, Tim. Try the following: eat low carb, low fiber, high protein (eg lots of meat) for three days - you won't poop much, you'll pee all the time and lose 5+ lbs.

    Your body is able to process food at a rate exceeding what you add. Otherwise, if eating exceeded processing ability you'd just slowly blow up and be full of ... ;)
  • Sued0nim
    Sued0nim Posts: 17,456 Member
    Interestingly (to me, and quite possibly highly irrelevant to anything discussed here but since I've lost weight my rate of defecation has increased from a couple of times a week to virtually daily

    I wonder what that has to do with .. sluggish bowel correction? better intake?
  • Azexas
    Azexas Posts: 4,334 Member
    rabbitjb wrote: »
    Interestingly (to me, and quite possibly highly irrelevant to anything discussed here but since I've lost weight my rate of defecation has increased from a couple of times a week to virtually daily

    I wonder what that has to do with .. sluggish bowel correction? better intake?

    (I've noticed the same pattern with myself) I've noticed since I've been tracking macros I'm getting more fiber than I was before. Could be why you noticed the change.
  • snowflakesav
    snowflakesav Posts: 649 Member
    The big weight loss is from burning stored glycogen in the the muscles. It isn't fat. Glycogen binds with several water molecules so when it is burned....big loss. the fewer carbs..the quicker this happens.

    I agree that a portion of the loss is probably waste.
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  • cwolfman13
    cwolfman13 Posts: 41,865 Member
    you lose a lot of glycogen (essentially water) and because you are eating less, you have less inherent waste in your system.
  • Orphia
    Orphia Posts: 7,097 Member
    Thanks, all!

    Very interesting stuff!

    (Did I just include poop as being interesting? :smiley: )
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