Why Diarrhea Happens After Fasting: Causes and Prevention Tips

Why Diarrhea Occurs After Fasting

Fasting has become an increasingly popular health and fitness trend in recent years. Advocates claim fasting helps with weight loss, reduces inflammation, improves cardiovascular health, and more. However, many people experience diarrhea and other digestive issues when fasting.

In this article, well explore the reasons why diarrhea and loose stools often occur after periods of fasting. Well also provide tips on how to prevent and treat fasting-related diarrhea.

What Happens During Fasting

Fasting is defined as going an extended time without eating food. This forces the body to shift into a metabolic state called ketosis, where it burns stored fat for energy instead of carbs from food.

There are several fasting protocols, including:

• Intermittent fasting - Cycling between periods of eating and fasting, like 16:8 or 5:2 plans
• 24-hour fasts - Going without food for a full day
• Extended fasts - Abstaining from food for multiple days
• Water fasts - Consuming only water during the fast

When you suddenly stop eating or dramatically cut calories, it triggers substantial changes in digestive function and gut bacteria balance. These fasting-induced gastrointestinal changes are the main reason diarrhea can occur.

Reduced Fiber Intake

Dietary fiber plays a key role in promoting healthy bowel movements. Soluble fiber absorbs water in the intestines to form a gel-like consistency. This helps bulk up and soften stool, allowing it to pass smoothly through the colon.

When fasting, fiber intake from foods like fruits, vegetables, whole grains, beans and nuts drops significantly or is eliminated. Less fiber leads to harder, drier stool that is more difficult to pass, causing straining and diarrhea.

Altered Gut Bacteria

Your gastrointestinal (GI) tract contains trillions of bacteria that play important roles in digestion, immunity and more. The types of foods you eat help determine the makeup of this gut microbiome.

Fasting triggers changes in your microbiome by reducing populations of bacteria that feed on dietary fiber and complex carbs. Beneficial strains like Bifidobacteria and Lactobacillus decline, while potentially harmful bacteria like Clostridium can overgrow.

These fasting-induced shifts in gut bacteria are thought to cause increased intestinal permeability (leaky gut), irritation of the GI lining, and diarrhea in some cases.

Dehydration

Maintaining adequate hydration is critical for proper digestive function. Water is necessary for the bowel to efficiently move and absorb waste.

Strict fasts where only water is consumed can lead to dehydration, especially if increased fluids are not ingested to compensate for lack of food. Dehydration thickens mucus secretions and hardens stool, resulting in constipation.

Paradoxically, severe dehydration can also cause the body to draw water from the stool, leading to loose, watery diarrhea. The colon tries to urgently flush out the concentrated waste.

Overactive Colon

Some fasting plans allow diet soda, coffee, tea or other calorie-free beverages. The artificial sweeteners and caffeine in these drinks can overstimulate the gastrointestinal tract.

Caffeine encourages colon contractions, while sweeteners like sorbitol pull water into the colon. This makes the colon push out its contents quicker, potentially causing urgent, watery stools.

Gallbladder Issues

The gallbladder releases bile to help break down and digest fat. When fasting, the gallbladder doesnt receive the same stimulation from food to empty its stored bile.

Excess bile buildup can cause diarrhea by accelerating colon motility and leading to bile acid malabsorption. Gallbladder problems are more likely during longer fasts when fat intake is very low.

Electrolyte Imbalances

Electrolytes like sodium, potassium and magnesium help regulate hydration levels and muscle function in the body. Restricting food intake can cause electrolyte deficits.

Low magnesium levels are commonly linked to loose stools and diarrhea. Potassium deficiency can also overstimulate the gut. Maintaining proper electrolyte balance is important to prevent fasting diarrhea.

How to Prevent Fasting Diarrhea

Use the following tips to help minimize the chances of diarrhea and digestive issues when fasting:

Break Your Fast Gradually

Dont go immediately from fasting to eating a large meal. Introduce foods gradually in smaller portions to give your GI tract time to readjust.

Choose Low-Fiber Foods

Temporarily opt for low-fiber foods like eggs, rice, toast, yogurt and chicken. Then slowly increase fiber again over a few days.

Stay Hydrated

Drink increased fluids like water and electrolyte beverages. Broths can also help replenish sodium and minerals lost when fasting.

Limit Caffeine and Sweeteners

Avoid diet soda, coffee and tea as much as possible when fasting to prevent colon stimulation.

Take a Probiotic

Probiotic supplements can help populate your gut with beneficial bacteria after fasting to improve digestive function.

Eat Fermented Foods

Kefir, kimchi, sauerkraut and yogurt provide probiotics plus fiber to feed gut bacteria.

Treating Fasting Diarrhea

If you do experience diarrhea after a fast, here are some effective remedies:

Activated Charcoal

Charcoal capsules can help absorb toxins or irritants in the GI tract causing diarrhea episodes.

Rice Water

Sipping small amounts of water strained from boiled rice can provide soothing starch to firm up loose stools.

Bismuth Subsalicylate

Products like Pepto-Bismol coat the intestines to ease inflammation and reduce motility to treat urgent diarrhea.

Probiotic Yogurt

Look for yogurts containing live cultures like Lactobacillus to help restore gut bacteria after fasting.

Fiber Supplements

Over-the-counter psyllium husk or methylcellulose can provide missing fiber to bulk and solidify stool.

Oral Rehydration Salts

Drink fluids containing electrolytes and glucose to rehydrate and alleviate diarrhea.

When to See a Doctor

In most cases, fasting diarrhea will resolve on its own within a day or two. But contact your doctor if you experience:

• Diarrhea lasting more than 2 days
• Fever over 101 F
• Bloody stool
• Severe pain or cramping
• Signs of dehydration like dizziness, rapid heart rate, dark urine

These can indicate a serious intestinal infection or health issue requiring medical treatment. Diarrhea lasting over 2 weeks may be a sign of chronic conditions like IBS, IBD or thyroid disorders.

Who Should Avoid Fasting

Fasting is not recommended for everyone. You should avoid fasting if you have:

• Diabetes
• Gastrointestinal disorders like ulcers or reflux
• A history of disordered eating
• Low blood pressure
• Nutrient deficiencies
• Liver or kidney conditions

Pregnant and breastfeeding women should never fast, as it can have serious effects on the baby. If taking prescription medications, consult your doctor before fasting as well.

The Bottom Line

Its quite common to get diarrhea after embarking on a fasting regimen. Sudden changes in food intake, fiber, gut bacteria, hydration and electrolytes create the perfect storm for fasting diarrhea.

Following proper preparation strategies can help reduce the likelihood of GI issues. Consuming probiotics, electrolytes, and fluids is key. Slowly transitioning out of a fast can prevent diarrhea when reintroducing foods.

If fasting diarrhea does strike, utilize natural remedies and over-the-counter medications to find relief quickly. Pay attention to any persistent or severe symptoms and seek medical help if warranted.

With the right approach, occasional fasting diarrhea shouldn't deter you from realizing the potential health benefits of fasting. Just be prepared and patient with your bodys adjustment to this dramatic dietary shift.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.