Appetite-regulating Effects of Dietary Fiber's Viscosity

Dietary fiber plays a potential role in regulating energy intake and stabilizing postprandial blood glucose. As an important physical property of soluble dietary fiber, viscosity is also a key contributor to its nutritional effect.

With the continuous deepening of people's research on dietary fiber, there are more understandings of the benefits of dietary fiber viscosity on human health. As an important texture factor of plant cells, soluble dietary fiber widely exists in various plant foods. In recent years, many studies have revealed the positive effects of high-viscosity dietary fiber in delaying gastric emptying, reducing food intake, stabilizing postprandial blood sugar, and hormone regulation. The viscosity properties of dietary fiber are expected to be used for appetite intervention.

Appetite regulation mediated by dietary fiber viscosity before eating.

Anticipated satiety is defined as the body's subjective appetite feeling caused by the texture properties of food before it is ingested, and it is considered to be one of the decisive factors in regulating food intake. Studies have shown that subjects' subjective feelings about food viscosity, texture and other properties before eating will trigger their associations with the satiety performance of food, including how much satiety food may bring, or to what extent people may resist hunger after consuming food. In addition to the flavor characteristics of the food itself, the textural properties of the food, including its viscosity, are considered to be the key factors that determine whether the food's expected satiety is strong or weak.

For example, studies have confirmed that solid and semi-solid foods can provide a stronger feeling of satiety than liquid foods under the same energy density conditions. McCrickerd recruited 24 subjects and used a three-factor eating questionnaire to study the effect of carrageenan beverages with different viscosities on expected satiety. The results of the study showed that the thick appearance of beverages imparted by viscous carrageenan had a greater impact on expected satiety. Under the same energy density conditions, high-viscosity carrageenan beverages can suppress hunger better than low-viscosity beverages.

Appetite regulation mediated by dietary fiber viscosity during oral processing.

Studies suggest that increasing the duration or intensity of oral exposure (oral and food contact) can promote satiety signals and help control subsequent energy intake. The degree of oral exposure is affected by the texture properties of food, and viscosity is one of the important physical properties that cannot be ignored. Studies have found that the viscosity of food has a significant impact on oral processing. High-viscosity foods rich in dietary fiber can promote chewing force and chewing rate, prolong oral exposure time, and increase the chewing cycle before swallowing. In addition, the texture characteristics of food ingested into the oral cavity, such as the mechanical stimulation of the viscosity of fluid foods on the oral cavity and the chemical stimulation of their flavor components, can promote the secretion of oral saliva and help enhance the body's satiety. 

Wanders conducted a randomized crossover trial of 121 subjects to explore the effect of viscous dietary fiber on satiety. The subjects were asked to eat biscuits containing cellulose, guar gum and alginate at will, and the results showed that compared with the control group, eating biscuits containing 5% alginate could finally reduce the subject's appetite by 22%. However, the biscuits added with guar gum and cellulose had no significant effect on the energy intake of subjects with random meals. In addition, biscuits containing alginate increased the oral exposure time by 48%, which is believed to be the key reason for a lower energy intake of the subjects.

Appetite regulation mediated by dietary fiber viscosity after eating.

The intervention of the viscosity properties of dietary fiber on the gastrointestinal digestion process is the key to its regulation of the body's appetite response. In short, the viscous dietary fiber increases the viscosity of the contents of the GI tract, thereby prolonging the transit and digestion of food in the GI tract. In this way, the viscous properties of dietary fiber help blunt the body's insulin response, stabilizing its postprandial blood sugar levels. In addition, soluble dietary fiber can be fermented in the colon, and the short-chain fatty acids produced can not only reduce the pH value of the colon, improve the structure of intestinal flora, but also help induce the body's satiety.