Welcome to The Fast Diet › The official Fast forums › Body › Science of intermittent fasting › fasting and urine output
This topic contains 23 replies, has 21 voices, and was last updated by Bronx 2 years, 3 months ago.
Viewing 24 posts - 1 through 24 (of 24 total)
24 Aug 13
IM definitely passing more urine on fast days. Why is that?
Because you are drinking more?
I have noticed this as well, especially during the night following a fast day. I definitely drink more on fast days, which obviously contributes, but I have wondered if there is something else going on.
I believe the breakdown of fat produces extra water, if my chemistry is correct! Take encouragement from this!
No i meant to say im not drinking more as that would have been the obvious conclusion. Thanks Kris i wondered if it was due to breakdown of fat. IM feeling dehydrated so definitely need to be drinking more fluid.
i heard 80% of fats cells are water, so i belive its due to fat breaking down. xx
25 Aug 13
Very interesting. I’ll keep an eye on these posts
28 Aug 13
This is good to know about the breaking down of fat. I find I need to go a couple of times the night of my fast before I go to bed which is unusual for me.
29 Aug 13
I’ve noticed that as well. I make point of drinking plenty, but the frequency of coming for a pee is defintely significantly higher. Very nice to hear its due to fat being broken down!
28 Nov 13
Thanks for the feed back. I have been on the diet for the last nine months with great success and need to urinate considerably more on diet days. I try and keep my liquid intake the same on diet days but confess to an extra 1/2 cups of coffee.
I have noticed i wee more if i am on any kind of diet,night time is the worst for me when i am trying to sleep,5 times i got up to wee last night lol although it is inconvenient at the time i just think their goes more calories.
29 Nov 13
@ James P
” I have been on the diet for the last nine months with great success and need to urinate considerably more on diet days. ”
Some have already said, that it’s because we drink more. True.
I have gone to two different doctors in different years specifically to be checked for frequent nocturnal urination.
Both charged me a fee, took tests, and told me to stop drinking water before going to bed at night. That’s it?
I only drink water and I enjoy it, fasting or no fasting. Most of the time, I sleep well through the night.
Here’s what I know that works and takes care of this excess water retention: Hot Bikrum Yoga.
This has a favorable effect on my wife, so I know it’s just not me only, and lasts for a couple of days.
The sweat secreted through every pour is cleansing, detoxifying, and eliminates nocturnal inconveniences.
It helps that winter is here and a sauna type of a workout is a gift and very welcomed.
2 Dec 13
I drink much the same on fast days as others but I find I need to go more on fast days. I’m happy to think it might be fat cells that I’m flushing away 😀
22 Jun 15
I have been on the 5:2 diet since April 2003 (just over 2 yrs). Male 70 yrs.
It quickly took my weight from around 98 Kg to 88 Kg and have been at this weight for about 15 months. So pleased, I am now reluctant to give it up, because I have every thing I want on non – diet days, including my regular tipple of Red Wine.
However, I have significant increased urination on my diet days (particularly the night of diet days).
I have to get up to urinate 4 to 6 times.
On non diet nights, I generally sleep through, or only have to get up once.
I do not drink more fluids on diet days, though I do use soups (in winter) for lunch because of convenience and satiation.
I was so pleased to see that others experience this increased urination, and I hope the theory about breaking down fat causing extra fluid is correct.
BTW, I mentioned this increased urination to my GP (Male 50Yrs), who is also on the 5:2 WOL, and he just put it down to his increased fluid intake on diet days.
26 Jun 15
Here is my understanding:
The body stores energy as glucose IN SOLUTION for instant short term energy, and converts excess glucose to fat for sustained energy. Fight or Flight – glucose for quick action for fighting, fat for fleeing.
The body can’t store much glucose because it is in solution – bulky and heavy. Fat is much better for storing energy (1 pound of fat is enough to run a full marathon!)
On a fasting day you are using glucose without replenishing it. The glucose (in solution in water) is used up and you pee a lot to get rid of the water. Once your glucose level has dropped your body is forced to start burning fat. You will notice that you then don’t pee as much and your urine is deep yellow (getting rid of the waste products from burning fat). This is a good sign – your body has switched to burning fat.
On a fasting day you can expect to lose 3 or 4 pounds in weight. Most of this is water. Some is having less stomach contents. Only about half a pound of it will be due to getting rid of fat.
The next couple of ‘binge’ days you will replenish your glucose levels, and will need to drink plenty of water as the glucose is held in solution in water.
After a couple of days your weight will have gone back up, but should be about half a pound less than before. Time to fast again and lose about 4 pounds (mainly water) all over again.
To monitor your weight you need a good pair of digital scales that measure to 0.2 lb (or less). Weigh yourself each morning before breakfast. Plot the results as a graph. You will see your weight yo-yo’ing up and down by about 4 lbs twice per week as your glucose (and water) level goes up and down. However you should be able to see a downward trend of about 1 lb per week as you burn fat.
If you are good with spreadsheets on your PC, you should be able to plot a graph and calculate a 7 day average. Every period of 7 days will have 2 fasting days and 5 binge days, so the 7-day average will eliminate the yo yo effect.
So to sum up, increased urination is due to using up the glucose in solution (not breaking down fat or drinking more). Breaking down fat makes your urine deep yellow. Replenishing your glucose levels after fasting needs water, so you will need to drink more AFTER fasting.
If you think 2 days of fasting is a hard way to burn off 1 lb of fat, the alternative is to burn off 1 lb of fat by running a full marathon!
27 Jun 15
Thank you PaulandCarol for taking the time to respond with such a detailed, plausible and logical explanation. I will be well armed next time I visit my GP!
I weigh myself most mornings before breakfast and I’m always around my 88 Kg plus or minus a few decimal points, after my “Diet” days.
Now, depending on “Binge” days intake, and amount of exercise (mainly lap swimming), on other days, the scales often reach 89 kg plus or minus a few decimal points.
I haven’t recorded on Excel as I mentally average the figures.
My wife would accuse me of having an OCD if I completed a daily Excel Sheet!!
Thank you again – I will be interested to see other 5:2 WOLifers comments!
P.S. Running a marathon is out of the question @ 70 yrs. of age!!
19 Oct 15
Your explanation is very re-assuring. I have been on the 5/2 for 10 months, and have not met anyone who comments on increased urination, especially at night. I also have cold feet on fast days, (but they are not cold to touch) and was beginning to wonder if I had diabetes, although tested 8 months ago and all clear.
To be honest it’s not hunger that I find difficult to manage its the need to pop to the loo. So I go to bed early on fast days, watch catch up TV, whilst intermittently nipping to the loo.
I have been doing 5:2 since April 2013, lost 28 kg and have been maintaining my healthy goal weight for well over 18 months. Frequent urination on fast days had always been an issue, especially at night. After about a year, I learnt to fast for 24 hours, saving all my 350-400 cals for an evening “meal”. This way my stomach has at least a little food in it to absorb (or mop up) some of the water I’m drinking. I now only get up a couple of times at night. Much better. PVE
22 Jan 16
I’m really pleased to see all these posts – I never thought to look before. I’m just coming back to 5+2 having tried it with success soe time ago. I too had noticed that I have to get up to pee a couple of times the night of my fast day. Sure enough, the first day I came back to 5+2 I was up twice. It’s no problem as I usually sleep well, and go back to sleep as soon as I get back into bed. Really useful to share all these earlier posts, and as I’m pretty sure I don’t drink much more on fast days, it’s good to think that it’s part of the beneficial effects of the fasting diet.
As well during fasting your salt intake in lowered thus less water retention
16 Jun 17
I been on low calorie diet and 3days zero food fast. I do pee a lot I drink tea and cofy and 1 litter water day. I pee least 3 to 5 times a nite and abt 5 times least in my 8 hour shift at work . So a anoing but I heard it can be water weight and also fat braking down. X
I lose abt 4.5pounds a week
Well, it is now 2017, I am now 72, and Im still using the 5:2 diet to control my weight and keep my IGF around 20 (as at Jan.’17).
My weight has crept up a little from around 88Kg to 92Kg, but I have had spinal surgery recently and this has caused me to put my daily swimming regime on hold for the last few months.
Frequent Nocturnal urination after the diet days (Mon & Thur) is still a real characteristic of this diet for me !! A small price to pay though for a fairly painless way to control weight & IGF !
I am 73 and following a fasting day I’ll be up at about 2am. When I first started this caper I asked why everyone said that rapid weight loss was water loss and Simcoeluv explained the science. Put simply, to burn an ounce of fat your body needs 3 to 4 ounces of water, and having used it there is only one place for it to go.
Surgery is a nuisance. After mine last year I was on restricted exercise for some months and that does not help!
I know what you mean, Penguin. Broke my leg in January and was unable to do my normal walking routine for a couple months. Even though I continued to fast I gained 8 pounds, and am struggling to lose it now. Part of it was I wasn’t exercising at all, and part was just sitting around the house on NFD I was eating too much. Old habits are hard to break.
I too find I have to urinate more on fasting days too. Always thought it was because I was drinking more.
You must be logged in to reply.
Username or Email:
Track your weight and measurements, BMI and TDEE with our new tracker.
The Fast books are available throughout the world and in many different languages. Buy a copy today.
Michael is touring Australia this September! Here's a link to dates and tickets. Hope to see you there.
Michael Mosley gives an update for 2019, current research in the field and announces a tour starting in February.
Michael looks at the Horizon special, "What's the Right Diet for You" and tells us which diet they say is best for him.
• All featured posts •
in Weight loss • updated 26 minutes ago by Penguinchick
in Weight loss • updated 28 minutes ago by Brads27
in Weight loss • updated 2 hours, 14 minutes ago by ccco
• All recent topics •
Copyright © 2019 Michael Mosley and Mimi Spencer
Technical questions or problems with the site? Please email our technical contact.