Does Fiber Help You Lose Weight? Dietary fiber has a role in managing several diseases shown in different clinical studies. We need high-fiber foods for our metabolism, digestive system, and gut health and to prevent related chronic diseases such as obesity.
The Food and Drug Administration defines dietary fiber as all carbohydrates that are neither digested nor absorbed in the small intestine. Dietary fiber effects depend on chemical characteristics[1] such as solubility, viscosity, and fermentability which determine the fiber functions in the body.
These functions can be related to digestive functions, micronutrient availability, gut transit time, stool formation, and microbiota profile. Altogether, these effects benefit different chronic diseases.
So how much fiber do you need? Researchers and specialists recommended a daily intake for adults of 25–35 grams of fiber per day. However, the average daily dietary fiber intake remains lower than 20 grams per day in adults worldwide.[2]
Does Fiber Help You Lose Weight?
A randomized controlled study[3] with obese adults assessed the predictor role of diet for losing weight. There were important changes in carbohydrate, fiber, and unsaturated fatty acids consumption from baseline; however, fiber intake was the most influential predictor for weight loss. In addition, high-fiber diets helped with adherence to the macronutrient prescriptions of the diet.
It is stated in many studies that following a diet high in carbohydrates and fiber while low in fat and calories, leads to weight loss and prevents diabetes[4] in high-risk individuals.
Another important result from an intervention study[5] showed that the calorie-restricted high-protein diet was less effective than the high-protein diet with the same calorie restriction and more fiber. Fiber supplements may lead to higher weight loss, body fat reduction, and induction of satiety.
What Are The Fibery Foods?
High fiber intake in the diet[6] is important for both weight loss and overall health benefits, and you can get fiber only from plant-based foods. Here is a high-fiber foods list with their fiber amounts per portion.
High-fiber fruit list
| Fruits | Serving size | Total fiber (grams)* |
|---|---|---|
| Banana | 1 medium | 3.0 |
| Apple, with skin | 1 medium | 4.5 |
| Pear | 1 medium | 5.5 |
| Raspberries | 1 cup | 8.0 |
| Orange | 1 medium | 3.0 |
| Strawberries | 1 cup | 3.0 |
High-fiber vegetable list
| Vegetables | Serving size | Total fiber (grams)* |
|---|---|---|
| Carrot, raw | 1 medium | 1.5 |
| Cauliflower, raw | 1 cup chopped | 2.0 |
| Sweet corn, boiled | 1 cup | 3.5 |
| Potato, with skin, baked | 1 medium | 4.0 |
| Brussels sprouts, boiled | 1 cup | 4.0 |
| Turnip greens, boiled | 1 cup | 5.0 |
| Broccoli, boiled | 1 cup chopped | 5.0 |
| Green peas, boiled | 1 cup | 9.0 |
High-fiber grain list
| Grains | Serving size | Total fiber (grams)* |
|---|---|---|
| Bread, rye | 1 slice | 2.0 |
| Bread, whole-wheat | 1 slice | 2.0 |
| Brown rice, cooked | 1 cup | 3.5 |
| Popcorn, air-popped | 3 cups | 3.5 |
| Oat bran muffin | 1 medium | 5.0 |
| Oatmeal, instant, cooked | 1 cup | 5.0 |
| Quinoa, cooked | 1 cup | 5.0 |
| Bran flakes | 3/4 cup | 5.5 |
| Barley, pearled, cooked | 1 cup | 6.0 |
| Spaghetti, whole-wheat, cooked | 1 cup | 6.0 |
High-fiber legume, nut, and seed list
| Legumes, nuts, and seeds | Serving size | Total fiber (grams)* |
|---|---|---|
| Sunflower kernels | 1 ounce | 3.0 |
| Pistachios | 1 ounce (49 nuts) | 3.0 |
| Almonds | 1 ounce (23 nuts) | 3.5 |
| Baked beans, canned | 1 cup | 10.0 |
| Chia seeds | 1 ounce | 10.0 |
| Black beans, boiled | 1 cup | 15.0 |
| Lentils, boiled | 1 cup | 15.5 |
| Split peas, boiled | 1 cup | 16.0 |
Fiber Solubility
The fiber characteristics[7] affect sugar and fat absorption, stool structure, and frequency. These functions help regulate the digestive system.
Solubility is the ability of dietary fibers to dissolve in water. Insoluble fibers remain as discrete particles in water. Soluble dietary fibers thicken[8] when they cross with water and have a role in the digestive tract concentration-dependent manner.
Dietary fiber intake also changes microbiota composition, stimulating the production of secondary metabolites such as short-chain fatty acids that are an important nutrient for beneficial bacteria in the intestine.
It is easier to access and metabolize soluble dietary fiber[9] for fiber-degrading microorganisms in the intestine than with insoluble dietary fiber. Soluble fibers help to produce beneficial and functional metabolites.
Here are the soluble and insoluble dietary fiber sources:[10]
| Soluble dietary fiber | Insoluble dietary fiber | |
| Types | Pectins, inulin, mucilages, glucomannan, ß-glycans | Cellulose, and hemicelluloses; and some types of resistant starch |
| Typical sources | Fruit, various berries, broccoli, sweet potatoes, other vegetables (carrots, beans, lentils), nuts, oats and barley, guar, psyllium | Whole-grain starches, tomatoes, cucumbers, legumes, nuts, almonds, brown rice, bran |
Fiber Fermentability
Some fermentable fibers function as prebiotics. Prebiotic is a term[11] for “asubstrate that is selectively utilized by host microorganisms conferring a health benefit”. Inulin-type fibers and galactooligosaccharides are prebiotic fibers.
Prebiotic fibers have a fermentative capacity and lead to the release of short-chain fatty acids. It is a substrate for stimulating the growth of beneficial bacteria,[12] as we mentioned above. In 2018, a systematic review and meta-analysis[13] of 64 randomized controlled trials demonstrated that fiber, especially fructans, and galactooligosaccharides, increases the Bifidobacterium and Lactobacillus, beneficial bacteria species, in microbiota.
How Does Fiber Work To Help You Lose Weight?
As you can see from the research results, fiber will help you lose weight, but how? What are the mechanisms that fiber provides for weight loss?
Digestive Effects
The health benefits of fibers are mostly related to the digestive system. Fiber intake[14] can increase the amount of food intake while reducing total energy intake because the energy density of higher-fiber foods is lower than low-fiber foods. Soluble fibers can increase the time in the stomach during digestion and delay or decrease sugar and fat absorption in the intestine.
This mechanism reduces both the absorption of calories and insulin secretion from the pancreas. Therefore fiber consumption is helpful for weight loss, blood sugar, and insulin control.
Digestive problems, mainly constipation, are major findings of people with high body weight. Therefore, regulating digestive problems and relaxing the bowels helps the management of body weight and increases the quality of life.
Fiber intake can decrease gut transit time, which means better constipation management and defecation frequency increment. Research conducted with healthy individuals[15] showed that an increased additional nine grams of wheat bran for three days compared to a low-fiber control diet significantly lowered gut transit time, also called gastric emptying.
Wheat bran supplementation[16] increased stool frequency from one per day to 1.5 cups per day. Other studies have shown that supplementation with cellulose–pectin combination,[17] short-chain fructooligosaccharides supplements,[18] and high-fiber breakfast cereals[19] also increase stool frequency. According to these effects, fibers can flatten your abdominal area and help you to lose belly fat.
Thermic Effect
You burn calories while you digest food called the thermic effect of food.[20] The meal volume (larger meal size) and the effort you give to digest are related to this calorie expenditure. Therefore, dietary carbohydrate with high fiber increases the thermic effect of foods. Thus, high-fiber, high-protein diets are perfect for increasing energy expenditure.
Appetite Control
When it comes to appetite control,[21] dietary fibers are our best supporters of us. Because fiber consumption, primarily soluble fibers, helps you hold a large amount of water and increase tension in the stomach wall, which triggers signals from the digestive system to the brain called vagal signals which give feedback to the brain about fullness and satiation. Also, you produce more short-chain fatty acids in the intestine if you consume dietary fibers that can be fermented by bacteria. Short-chain fatty acids also decrease your hunger and control your appetite with the stimulation of the secretion of special peptides in the intestine to suppress appetites, such as cholecystokinin, glucagon-like peptide-1, peptide YY, etc. These molecules also go to the brain and say you are done with eating.
What Does Fiber Help With?
People with high weight generally have impaired blood sugar control, increased blood fat and cholesterol levels, and constipation are common in them. Dietary fibers help you to lose weight by reducing obesity-related outcomes or improving your overall health by eliminating these health problems.
Blood Sugar And Insulin Control
A review[10] of large prospective cohort studies indicated that consumption of more than 28 grams per day for women and 38 grams for men of insoluble cereal fibers or whole-grain products might reduce insulin resistance and type-2 diabetes risk by 20–30%.
Effects On Blood Fats And Cholesterol Excretion
Water-soluble viscous-forming dietary fibers help to reduce[22] total and low-density lipoprotein cholesterol (bad cholesterol) levels by about 5-10%. High-fiber foods, such as oats, barley, legumes, flax seeds, apples, and citrus foods, show cholesterol-lowering benefits.
Dietary fibers have a role in the excretion of bile[23] and cholesterol in the stool. It is an essential mechanism for both high blood cholesterol and fatty liver disease.
Help To Get Rid Of Constipation
A systematic review and meta-analysis[24] of seven studies concluded that fiber consumption is an effective treatment for chronic constipation in adults compared with a placebo. These studies showed that dietary fiber such as wheat bran, supplement forms such as psyllium, and prebiotics such as inulin increased stool frequency and normalized stool consistency.
Side Effects Of Using Fiber For Weight Loss
Fiberous products contain phytates[25] that reduce the absorption of dietary minerals such as iron, zinc, and calcium. But also, several human studies have shown that specific fibers, such as fructans[26] and galactooligosaccharides,[27] may increase dietary calcium absorption.
If you have inflammatory bowel diseases such as Crohn’s or ulcerative colitis, or irritable bowel syndrome, you should consult your doctor about your dietary fiber intake. Because in such cases, the gut and microbiota may not function normally and may affect how you tolerate dietary fibers. Also, some dietary approaches, such as a lectin-free diet, restrict several high-fiber foods due to other structures these foods contain.
Final Thought
Does Fiber Help You Lose Weight? Dietary fiber is a potent diet strategy for weight loss, as it is in many ways for health promotion. It helps you control your appetite by transmitting satiety signals from the digestive system to the brain.
It positively supports bacterial diversity in the microbiota, which is associated with many diseases. In addition, it provides blood sugar and insulin regulation by prolonging the digestion and absorption times while also binding and removing some fat and cholesterol.
All these are functional mechanisms for weight loss. However, it is beneficial to choose the fiber sources that you consume with your doctor and registered dietitian, considering your health status.
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