Fiber is a dietary component that most people are deficient in. In fact, research shows, the average American consumes only half the amount of fiber they should get on a daily basis. One of the purported benefits of fiber is it crushes food cravings, especially for sugary foods with empty calories and little nutritional value. We could all stand fewer of those! But, not all fiber is equal for reigning in appetite and suppressing cravings. In fact, there’s one particular type of fiber you need more of to reduce your appetite and feel fuller after a meal.
Types of Fiber
Fiber falls into two main classes – soluble and insoluble fiber. Soluble fiber gets its name from the fact that it easily dissolves in water. In contrast, insoluble fiber does not. Soluble fiber is the form of fiber linked with a lower risk of cardiovascular disease while insoluble fiber is important for promoting bowel regularity. How does insoluble fiber keep you regular? By bulking up the stool and by increasing the transit time of food through the intestinal tract.
Of the two forms of fiber, soluble fiber has the more pronounced impact on appetite – and one type of soluble fiber is the best at quieting hunger pangs and it’s called viscous fiber. Studies show that a fiber’s viscosity is what makes it satiating. What is viscosity? In a physical sense, viscosity is a material’s resistance to flow. For example, maple syrup is more viscous than water, as it sticks to surfaces and is more resistant to flow. Plus, it’s thicker and has a more substantial texture. Some fibers, when they interact with liquid in the digestive tract, become more viscous – and it’s this property that aids in satiety. Viscous forms a thick gel that moves through the digestive tract more slowly and when food stays in your stomach and upper digestive tract longer, you feel fuller longer.
Yet, viscous food sources of fiber may suppress appetite in another way. When a meal is higher in fiber, it takes more effort and time to chew. This slows down the pace of a meal and when you eat slower, you often eat less. That’s because appetite-suppressing hormones kick in in about twenty minutes and if you leisurely ate your meal, you have more still on your plate when the appetite hormones tell you to stop eating. High fiber foods also have a different sensory quality than processed, low-fiber foods do. We tend to tire of eating foods high in fiber more than we do highly palatable, refined foods.
What Does Science Say about Fiber and Satiety?
Interestingly, a 2013 review study looking at appetite and fiber intake found that 39% of fiber treatments reduced appetite, a subjective measure, but only 22% of fiber treatments actually lessened food intake. So, you might feel fuller after eating a meal with fiber, but it doesn’t necessarily mean you’ll eat less. The ones that are most effective for curbing appetite and food consumption are fibers that are more viscous in nature.
So, it may not be accurate to say that all fiber decreases appetite. Yet, even insoluble fiber may have SOME appetite-reducing benefits. In a study published in the Journal of Clinical Nutrition, researchers found that 33 grams of insoluble fiber with a meal reduced appetite and food consumption when the participants ate a meal 75 minutes later. Plus, it had the added benefit of lowering the blood sugar response to the meal. Insoluble fiber is most abundant in whole grain foods, nuts, wheat bran, and vegetables.
How to Get More Viscous Fiber
By now, you’re probably wondering how to get more viscous fiber in your diet. Some whole foods that are rich in viscous fiber include beans, lentils, nuts, flaxseed, oat bran, Brussels sprouts, barley, and asparagus. Apple peels are rich in pectin, a type of soluble, viscous fiber. Psyllium husks are another excellent source of viscous fiber. So, a bowl of oatmeal or barley with ground flaxseed and nuts would be a good way to start the morning if you want to stay full longer. Add a source of protein as well to further enhance satiety.
In reality, whole grain foods, nuts, seeds, vegetables, and legumes are often a blend of soluble and insoluble fiber. Rather than obsess over getting viscous fiber, focus on eating more fiber-rich foods in general and making smart substitutions. Switching, fiber-rich whole grain bread for white bread and munching on nuts instead of chips is a simple way to boost your fiber intake and eat a more nutrient-dense diet. Eat more of the foods most of us don’t get enough of, like beans and lentils, too.
Don’t forget, recommendations are that women consume 25 grams of fiber daily and men around 38 grams. Most people fall short! How about you?
Other Health Benefits of Fiber
A diet high in fiber may lower the risk of cardiovascular disease, according to one study, by 40%. Meals high in soluble fiber are absorbed more slowly and lead to a more subdued rise in blood sugar after a meal. That’s a positive for metabolic health. Plus, some types of fiber have prebiotic activity, meaning they foster the growth of healthy gut bacteria. These bacteria produce acids that help keep the lining of your intestinal tract health and play a role in other function, including inflammation and immunity and mood. 70% of your immune system lies in your gut!
The Bottom Line
So, what can we conclude about fiber and appetite? Viscous fiber is the most effective for promoting satiety, but all forms of fiber have some health benefits. We find fiber naturally only in plant-based foods, so enjoy more of nature’s abundance – fruits, vegetables, nuts, whole grain, legumes. When you eat fruits and vegetables, buy organic and consume the peel as well, as the skin is a good source of soluble and insoluble fiber. The take-home message is to enjoy a variety of whole, fiber-rich foods with every meal.
Nutr Healthy Aging. 2017; 4(2): 157–168.
The Journal of Nutrition, Volume 130, Issue 2, 1 February 2000, Pages 272S–275S.
J Am Coll Nutr. 2013;32(3):200-11. doi: 10.1080/07315724.2013.791194.
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