The Real Poop About Intermittent Fasting And Constipation

When starting intermittent fasting, constipation may occur. Increasing fiber and water intake helps. This resolves quickly.
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Some women notice bloating, belly aches, unpleasant changes to their stool, and difficulty with bowel movements during the first few weeks of starting intermittent fasting.

This quickly resolves itself. Increasing fiber in your diet slowly, drinking more water, and moving your body more are just a few things you can do to make sure intermittent fasting and constipation isn’t a problem for you.

Written by
Jill Lebofsky
15+yr Women's Wellness Expert, Holistic Menopause Support, Intermittent Fasting, Midlife, Essential Oil, Author, Speaker

It is not exactly dinner conversation, but the poop talk is necessary if you start intermittent fasting.

Supporting your digestive system as it adjusts to your new intermittent fasting eating schedule will ensure “bathroom time” is easier and more productive.



Constipation refers to changes to your stool and difficulty eliminating your fecal waste.

Constipation can cause stomach discomfort, embarrassing odors, and pain when eliminating.


How do you know you are constipated?

Everyone has some minor digestive issues now and then, but here are signs to let you know you are experiencing constipation (1):


  • Difficulty or straining with elimination
  • Hard, small, or lumpy stools
  • Don’t have a bowel movement for more than 3 days in a row
  • Fewer than 3 bowel movements a week
  • After going to the bathroom, feeling like you still have poop left inside
  • Bloating 


Why do you get constipated?

Toilet paper.

 There are many reasons you may get constipated, and there may be more than one cause, including:


1. Slow-moving bowels

2. Dehydration

3. Medicine/Supplements

4. Changes in nutrition

5. Lifestyle changes (pregnancy, getting older)

6. Stress levels

7. Gastrointestinal disorders

8. Health issues

9. Travel

10.  Ignoring the urge to go



Does intermittent fasting cause constipation?

When doing any method of intermittent fasting, temporary constipation may occur in the first few weeks. This usually resolves itself as your body adjusts to consistent fasting.

When you do intermittent fasting, you allow the body time away from any nutrients, which it is not used to, often resulting in changes to your stool which may cause it to be hard, dry, and misshapen. It also affects the frequency of your bowel movements.

In addition, you are making dietary changes. Some of the best foods to eat when intermittent fasting are foods high in fiber. Your body may not be used to the additional fiber. Fiber adds bulk to your stools. Too much fiber can cause hard stools, making it difficult for fecal matter to pass, especially if you are not drinking enough water.


When you begin intermittent fasting, you lose a lot of sodium and water in your urine (2). Dehydration can easily occur if you aren’t mindful of your water intake. In addition to needing to drink more water to offset the extra fiber you’re consuming; you are generally used to taking in much of your hydration when you eat.

While following any type of fasting, you are eating fewer meals, which are often the only times people drink liquids.

You also get a large part of your hydration from water-packed foods, which, again, you are consuming less often.

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Am I not losing weight on intermittent fasting due to constipation?

Constipation itself doesn’t cause weight gain or prevent weight loss, although the scale may show a different story in the first few weeks for some people. Once your bowel movements are normal again and the waste build-up is gone, you will have a more accurate reflection of your weight and how intermittent fasting is working for you.


What helps against constipation?

Woman in underwear leaning her head against the bed.

Constipation during intermittent fasting isn’t inevitable. You can take measures when adopting an intermittent fasting lifestyle to prevent constipation or improve it if it’s occurring.


  • Stay hydrated throughout the whole day. Three to four liters of water is best.
  • Eat 25-30 grams of fiber daily, building up slowly by 5 grams per day.
  • Avoid processed foods.
  • Reduce dairy intake.
  • Drink coffee to stimulate the bowels.
  • Limit alcohol.
  • Increase physical activity to move the bowels.
  • Take magnesium supplements (3).
  • Talk with your doctor about any medication you may be taking that causes       constipation.
  • Don’t rush things on the toilet. Relax and give your body time to do its thing.
  • Go to the bathroom when your body tells you it is time, don’t wait.
  • Manage your stress.


Seek help

If your signs of constipation don’t quickly resolve themselves and you have been constipated for more than 3 weeks, or if you see any blood in your stool, or if you have rapid and unexplained weight loss (safe weight loss with intermittent fasting is 1-2 pounds a week), call your doctor immediately.


The takeaway

Some people do experience mild constipation in the first few weeks of starting any form of intermittent fasting due to changes in diet, changes in eating schedule, and decreased water intake.

Move your body more, drink plenty of water and eat less dairy and processed foods for added digestive support. The discomfort should resolve itself quickly but consult your doctor if you continue to experience difficulties with intermittent fasting and constipation.


1. Symptoms & Causes of Constipation. National Institute of Diabetes and Digestive and Kidney Diseases. 2018.

2. Phillips MCL. Fasting as a Therapy in Neurological Disease. Nutrients. 2019;11(10):2501. Published 2019 Oct 17. doi:10.3390/nu11102501

3. O’Neill, T. Magnesium for constipation. Michigan Medicine. 2021.

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