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How Long Does it Take the Body to Adjust to a High Fiber Diet?

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One of the best things you can do for your health and wellbeing is to increase the amount of fiber in your diet. Fiber is an important nutrient because of the many benefits it provides, including improved digestion, cardiovascular health, and weight control. Yet, switching to a high-fiber diet, especially if you've been eating a low-fiber diet previously, can be difficult. This article will define fiber, explain why it's important, and provide tips for adjusting to a high-fiber diet.

What is Fiber and Why Do We Need It?

Fiber is a type of carbohydrate that our bodies can't digest. Instead, it passes through our digestive system largely intact. There are two types of fiber: soluble and insoluble. Soluble fiber dissolves in water and forms a gel-like substance in the digestive tract, which helps slow down digestion and absorption of nutrients. Insoluble fiber, on the other hand, doesn't dissolve in water and adds bulk to stools, helping to prevent constipation.

We need fiber for a variety of reasons. Firstly, fiber helps keep our digestive system healthy and regular. A high-fiber diet can help prevent constipation and other digestive problems, including diverticulitis and hemorrhoids. Secondly, fiber can help lower our risk of heart disease by lowering cholesterol levels and improving blood pressure. Finally, fiber can also help with weight management by keeping us feeling full and satisfied for longer periods, leading to fewer cravings and less overeating.

Short-Term Effects of a High Fiber Diet

When you first start a high-fiber diet, you may notice some short-term effects. These can include drinking more water, having different bowel movements, feeling bloated, and having gas. This is because fiber absorbs water, which helps soften stools and makes them easier to pass. But if you're not used to eating a lot of fiber, this can cause some temporary discomfort. These effects usually go away after a few days as your body adjusts to the new diet.

If you're experiencing discomfort, there are some tips that can help. For example, make sure you're drinking plenty of water to help move fiber through your digestive system. You can also try eating smaller, more frequent meals to help your body adjust to the higher fiber intake.

Long-Term Effects of a High Fiber Diet

In the long term, a high fiber diet can have numerous health benefits. Some of the most significant benefits include reduced risk of chronic diseases, improved digestion, weight management, and a healthier gut microbiome. For example, a high fiber diet has been shown to reduce the risk of heart disease, stroke, and some types of cancer. Fiber can also help lower blood sugar levels and improve insulin sensitivity, making it a valuable tool in the prevention and management of diabetes.

Consuming a diet high in fiber can aid digestion by promoting regular bowel movements. Constipation and other digestive problems may be avoided as a result. A high-fiber diet is associated with a healthier microbiome because it encourages the growth of beneficial bacteria in the gut. Finally, fiber can aid in weight management because it reduces hunger and satisfies hunger for longer.

How Long Does it Take to Adjust to a High Fiber Diet?

Age, gender, general health, and one's current diet all play a role in how quickly one can adjust to a high-fiber diet. It may take a few days up to a week or more for your body to adjust to a high-fiber diet. 

Some tips that can help make the adjustment process easier include starting slowly and gradually increasing your fiber intake, drinking plenty of water, and choosing fiber-rich foods that you enjoy. Starting slowly can help your body adjust more easily to the increased fiber intake and reduce the likelihood of discomfort. For example, you can start by adding one high fiber food to your diet per day, such as a piece of fruit, a serving of vegetables, or a handful of nuts or seeds. Over time, you can gradually increase the amount of fiber in your diet until you're meeting your daily needs.

Drinking plenty of water is also crucial when you're increasing your fiber intake. Fiber absorbs water, which helps to soften stools and prevent constipation. Aim to drink at least 8-10 glasses of water per day to help your body process the extra fiber.

Finally, choose fiber-rich foods that you enjoy. There are plenty of delicious and nutritious high fiber foods to choose from, including whole grains, fruits, vegetables, legumes, nuts, and seeds. Experiment with different recipes and cooking methods to find new ways to incorporate fiber into your diet. By choosing foods that you enjoy, you'll be more likely to stick with your new high fiber lifestyle in the long term.

What Happens When You Start Eating More Fibre?

Increasing your fiber intake can have a number of positive effects on your body. Here are some of the changes you may experience when you start eating more fiber:

Improved digestion: Fiber helps to keep your digestive system running smoothly by adding bulk to your stool and promoting regular bowel movements.

Lowered cholesterol levels: Soluble fiber can help to lower your cholesterol levels by binding to cholesterol in your digestive system and removing it from your body.

Reduced risk of chronic diseases: A high fiber diet has been associated with a reduced risk of chronic diseases such as heart disease, diabetes, and certain types of cancer.

Increased feelings of fullness: Fiber helps to slow down the digestion process, which can help you feel fuller for longer and reduce your overall calorie intake.

Healthier gut microbiome: Fiber is the primary food source for the beneficial bacteria in your gut, which can have a positive impact on your immune system and overall health.

Tips for Incorporating More Fiber into Your Diet

There are some easy ways to add more fiber to your diet. Here are a few to start with:

  • Start Slowly

As mentioned earlier, starting slowly can help your body adjust more easily to the increased fiber intake. Start by adding one high fiber food to your diet per day and gradually increase from there.

  • Choose Whole Grains

Swap out refined grains for whole grains, which are higher in fiber and other nutrients. Choose whole grain breads, cereals, pasta, and rice to help boost your fiber intake.

  • Snack on Fruits and Vegetables

Fruits and vegetables are excellent sources of fiber and make great snacks. Keep a variety of fresh and frozen fruits and vegetables on hand for easy and healthy snacking.

  • Add Legumes to Your Diet

Legumes, such as beans, lentils, and chickpeas, are high in fiber and protein. Add them to soups, stews, salads, and side dishes for a nutritious and filling meal.

  • Choose Nuts and Seeds

Nuts and seeds are high in fiber, healthy fats, and other nutrients. Sprinkle them on top of salads or oatmeal, or snack on them between meals.


Adding more fiber to your diet can be good for your health in many ways, but it can be hard to adjust to a high-fiber diet. Start slowly, drink a lot of water, and choose fiber-rich foods that you enjoy to make the transition easier. Over time, eating a lot of fiber can help lower your risk of chronic diseases, improve your digestion, help you stay at a healthy weight, and make your gut microbiome healthier. By using these tips and tricks, you'll be able to add more fiber to your diet and get all the benefits of a high-fiber lifestyle.

Aaron Bernstein, MD, MPH

Aaron Bernstein is the Interim Director of The Center for Climate, Health, and the Global Environment, a pediatrician at Boston Children’s Hospital, and an Assistant Professor of Pediatrics.

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