August 30, 2023 • 6 min read
Diarrhea After Fasting: Causes, Solutions, & Prevention
Published on August 30, 2023 |
Update on August 29, 2023
MS, Registered Dietitian, Former President of CT Academy of Nutrition & Dietetics
Does fasting cause loose stools? Read on to learn whether it is normal to get diarrhea after fasting and what you can do with it immediately.
Table of Contents
Intermittent fasting has gained popularity as an effective method of shedding pounds. In addition to weight loss, it has been proven to bring about numerous health benefits [1].
However, as with any other dietary intervention, intermittent fasting can lead to certain side effects in some—especially in the initial phases. Diarrhea after fasting is one such side effect that you might have experienced.
Can intermittent fasting cause diarrhea, and is it normal to get diarrhea after fasting? Today, we are going to answer these questions and discuss how you can treat—or better yet, prevent fasting-related diarrhea.
There is almost no scientific data that links intermittent fasting and diarrhea, which hints that diarrhea is not a normal side effect of fasting.
However, a few people report that they experience episodes of diarrhea after intermittent fasting, which can make fasting quite an ordeal.
While diarrhea while fasting is not an uncommon occurrence, it’s not a universal phenomenon either. It’s also not a reason to quit intermittent fasting altogether.
Diarrhea is more likely your body’s way of reacting while it’s getting used to the new eating regime. For most people, diarrhea happens not during fasting but after they have had their first meal that breaks the fast.
Several factors, including meal composition, hydration levels, and coffee intake, can be the cause of loose stools after fasting.
The short answer to this question would be no. Fasting does not directly cause diarrhea.
Nevertheless, it conditions your digestive system in a way that makes it more prone to diarrhea. While you’re fasting, your digestive system slows down, and if you break your fast with foods that take a lot of effort to digest, it might cause digestive issues such as diarrhea.
Here are a few reasons that can trigger diarrhea after fasting:
As we mentioned just now, your digestive system is at rest after fasting for several hours. Foods that are hard to digest (such as high-fat, high-fiber food) can place a lot of strain on your digestive system.
When fatty foods are not properly digested, they can stimulate the colon to secrete excess fluids and cause diarrhea. Some people also might get diarrhea after eating spicy foods [2].
High amounts of fructose have been linked to diarrhea as well as artificial sweeteners such as sugar alcohols [2].
Since you know you’re allowed to drink zero-calorie beverages like coffee during fasting, you might have reached for the coffee pot more often than recommended. Coffee is a natural laxative that can stimulate your bowel function [3], and drinking too much can result in multiple trips to the bathroom.
Some supplements, such as Vitamin C [4] and magnesium [5], can induce diarrhea if taken in high doses.
While it is important to keep hydrated while you’re fasting, drinking too much water can cause electrolyte imbalances that can result in diarrhea [6].
Certain medications you’re taking, such as antibiotics and antacids, can cause diarrhea [7].
The most likely reason to have diarrhea after breaking your fast is that your digestive system can’t handle the meal you eat immediately after fasting.
After being inactive for hours, your body needs time to start digesting food again. Because of this, you’ll want to carefully choose the foods that are easy to digest as the first meal after fasting.
Eating large meals or fatty meals that are hard to digest immediately after fasting might lead to loose stools.
As we already explained, fasting does not cause diarrhea, nor does eating once a day. While eating once a day might lead to stomach discomfort due to bouts of hunger, it is not a likely cause of diarrhea.
If you experience loose stools after fasting, there are some immediate treatments you can try at home.
Most of the time, diarrhea is self-limiting and goes away within a few days. However, if the condition persists for longer than that and seems to worsen, you should consider consulting a doctor.
Additionally, if you notice blood in your stools or are experiencing other symptoms such as fever, it’s best to seek medical support.
You can prevent an upset stomach while intermittent fasting by keeping an eye on your diet.
Go for easy-to-digest foods like crackers, toast, and soup to break your fast.
Small meals allow your stomach to adjust and thus slowly stimulate your digestion.
Coffee can trigger bowel movements, so keep an eye on your coffee intake during your fasting window as well as the eating window.
Hydration during fasting is important, but don’t drink too much water as it can lead to electrolyte imbalances that can cause loose stools. The average daily fluid recommendation for men is 15.5 cups (3.7 liters), and for women, 11.5 cups (2.7 liters) per day [9]. For more personalized recommendations, consult with a registered dietitian.
Ask your doctor if the supplements and medications you take can lead to an upset stomach. Discuss with them about changing the medication schedules if they are likely to cause diarrhea after fasting.
This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!