“Fiber is an important part of a healthy diet and helps with weight loss” – I am sure you have heard this before, but what is exactly its role?

Understanding fiber

“Dietary fiber”, or what we commonly call “fiber” is a carbohydrate present in plants, and products from plants, such as cereals, fruits and vegetables.


This carbohydrate escapes digestion in our body by certain substances (enzymes).  The fiber then passes through the stomach, small intestine without being absorbed, and when it reaches the colon, it is fermented by gut bacteria, producing gases and a certain type of fats (short-chain fatty acids). This components formed have several roles in the body, described further, and depend on the type of fiber ingested.

There are two classifications of fiber, based on its solubility and each type helps the body in different ways. It is important to understand that both types are found in fiber-containing foods, and consuming the right amount of fiber is more important that worry about the type that is being ingested (unless you have a digestive disorder such as irritable bowel syndrome (IBS), in this case you should ask your GP or a dietitian for advice).

Types of fiber

Soluble fiber

Soluble fiber dissolves in water and usually forms a gel that slows the digestion and absorption of nutrients, such as sugars, by keeping the stomach fuller longer. This process has been described as being beneficial to helping with stabilising blood sugar levels and relieving constipation.

Foods containing soluble fiber include:

oats, barley and rye

– fruit, such as bananas mangos and apples

– pulses, such as dried beans, lentils, peas and chickpeas

– root vegetables, such as carrots and potatoes

– nuts and seeds, such as golden linseeds and flax seeds

How does fiber help with weight loss

Insoluble fiber

Insoluble fiber does not dissolve in water. Instead, it draws water to the intestine, increasing the stool volume and intestinal transit time, affecting nutrient absorption (e.g. reducing cholesterol absorption). This prevents constipation and promotes regular bowel movements, which of course has a positive effect on weight loss.

Another benefit of insoluble fiber is that it prevents the growth of undesirable bacteria in the gut (responsible for producing cancerous cells), and at the same time it promotes the death of pro-cancer cells already formed.

Foods containing insoluble fiber include:

– wheat and corn bran and whole grain products such as wholegrain cereals,  wholemeal bread, brown rice and pasta

– dark leafy vegetables, green beans

– nuts and seeds (except golden lineseeds)

– skin of fruits and vegetables.

Now that we know why we should eat fiber, let’s see what the right amount is.

Recommended daily fiber intake

The recommended amount is 25g per day for healthy adults – studies show that on average, people in the UK don’t get enough fiber, consuming only 15g of fiber daily.

Flax seeds - good source of fiber for weight loss

Benefits of fiber

Weight Loss

Fiber helps food to pass through the digestive system at a slower rate, reducing the absorption of sugars and fats, and what leading to a feeling of fullness, helping reduce the amount of calories consumed and reducing body weight or preventing weight gain.

Digestive disorders

Helps to prevent constipation, diarrhea and irritable bowel syndrome, and plays a role on preventing other complications, such as diverticular disease and hemmorhoids.

Diabetes and Cardiovascular disease

Helps to regulate the absorption of micronutrients and to stabilise glucose and cholesterol levels – lowering the chances of developing type 2 diabetes and heart disease.


Fiber may possibly help to prevent some forms of cancer, such as colon and rectum.

WatchFit Experts change lives!

And they can do the same for you.


Pollyanna Hale Health and Lifestyle coaches
Lost 13 Kg in Total
Mel, 32y Location: London, United Kingdom Working with Pollyanna changed everything. I lost 13kg, got toned and have more energy than ever! Get same results!


Chriz Zaremba Fitness Consultant
Lost 45 Kg in Total
Chris, 50y Location: London, United Kingdom Lost 45kg after the age of 50 and now competes and wins physique competitions and runs marathons Check our weight loss plans