**6. Gut microbiome functions**

The gut microbiome is involved in multiple physiological functions (**Table 1**) [32, 36–41].


#### **Table 1.**

*Physiological functions of gut microbiome.*

#### **6.1 Protection against pathogens**

Gut microbiome can protect against pathogens by killing or inhibiting unwanted organisms (e.g., *Clostridium difficile* genera) that are competing for nutrients.

#### **6.2 Regulation of immune system**

Gut microbiome regulates immune system by influencing the production of cytokines and antibodies.

#### **6.3 Regulation of metabolism**

Gut microbiome is involved in several metabolic processes. These processes include regulation of energy homeostasis and body weight, production of shortchain fatty acids (following fermentation of nondigestible fibers) and vitamins (vitamins B, vitamin K) [32, 36], glycemic control [37, 38], interaction with incretins [39], and metabolism of lipids [40] and bone [41].

#### **7. Gut microbiome in diseases**

Dysbiosis is observed in several medical conditions including obesity, malnutrition, type 2 diabetes, inflammatory bowel diseases, neurological disorders, and cancer [33, 42–48]. The dysbiosis can be the cause and/or the consequence of these diseases.

Gut microbiome influences drug pharmacokinetics and bioavailability, and thus, affects the efficacy and safety of several drugs used to treat diseases [49].

#### **8. Gut microbiome and obesity**

#### **8.1 Gut microbiome composition in obesity**

Although there are some conflicting data, most studies have reported that in obesity, there is a lower gut microbiome diversity, a higher abundance of Firmicutes

**261**

*Gut Microbiome in Obesity Management DOI: http://dx.doi.org/10.5772/intechopen.91974*

obesity [50].

*8.2.1 Diet*

**Table 2.**

*8.2.2 Prebiotics*

soybean).

*8.2.3 Probiotics*

*Lactobacillus* (genus belonging to Firmicutes phylum).

**8.2 Gut microbiome in obesity management**

using different tools (**Table 2**) [20, 21, 50–60].

**Tool for gut microbiome manipulation Description**

Probiotics Yogurt, cheese, milk

*Different tools used for gut microbiome manipulation in obesity management.*

Bariatric surgery Roux-en-Y gastric bypass Fecal microbiota transplantation Addition of healthy stool

Diet Low calories, low fat, high fiber Prebiotics Inulin, lactulose, resistant starch

Synbiotics Combination of prebiotics and probiotics

phylum, a lower abundance of Bacteroidetes phylum, and a higher Firmicutesto-Bacteroidetes phyla ratio [33, 42–45]. There is also a higher abundance of

According to most studies, the low-grade inflammation stimulated by lipopolysaccharide production is the prime mechanism by which gut microbiome induces

Gut microbiome can be manipulated for the purpose of obesity management

Diet is an important factor for the manipulation of gut microbiome and management of obesity. The amount of daily caloric intake and the content of food significantly affect gut microbiome but with high interindividual variability [20, 21, 51]. A diet that is low in calories, low in fat (< 20% of total macronutrients), and high in fiber (≥ 30 g/day) has a favorable effect on gut microbiome (increase in richness, decrease in Firmicutes-to-Bacteroidetes phyla ratio) and weight control (weight loss).

Prebiotics are chemicals (nondigestible food ingredients) inducing growth and/ or activity of bacteria [50, 52]. Prebiotics must be able to resist gastric acidity, resist enzymatic hydrolysis, resist absorption in the upper gastrointestinal tract, and be fermentable by the gut microbiome. Examples are inulin, lactulose, and resistant starch. Prebiotics can be found in many foods (e.g., leek, asparagus, onion, and

By modulating gut microbiome and lowering the production of lipopolysac-

Probiotics are nonpathogenic living microorganisms with direct or indirect effect on gut microbiome [50, 54, 55]. Products containing probiotics should be

charide, prebiotics have the potential to manage obesity. In a double-blind, placebo-controlled clinical study, administration of oligofructose-enriched inulin (8 g/day) to overweight/obese children for 16 weeks caused a significant increase in *Bifidobacterium* (genus belonging to Actinobacteria phylum) and significantly

slowed the body weight gain compared with placebo [53].

#### *Gut Microbiome in Obesity Management DOI: http://dx.doi.org/10.5772/intechopen.91974*

phylum, a lower abundance of Bacteroidetes phylum, and a higher Firmicutesto-Bacteroidetes phyla ratio [33, 42–45]. There is also a higher abundance of *Lactobacillus* (genus belonging to Firmicutes phylum).

According to most studies, the low-grade inflammation stimulated by lipopolysaccharide production is the prime mechanism by which gut microbiome induces obesity [50].

#### **8.2 Gut microbiome in obesity management**

Gut microbiome can be manipulated for the purpose of obesity management using different tools (**Table 2**) [20, 21, 50–60].


**Table 2.**

*Weight Management*

[32, 36–41].

**Table 1.**

**Function of gut microbiome**

**6. Gut microbiome functions**

**6.1 Protection against pathogens**

*Physiological functions of gut microbiome.*

**6.2 Regulation of immune system**

cytokines and antibodies.

**6.3 Regulation of metabolism**

**7. Gut microbiome in diseases**

**8. Gut microbiome and obesity**

**8.1 Gut microbiome composition in obesity**

tins [39], and metabolism of lipids [40] and bone [41].

The gut microbiome is involved in multiple physiological functions (**Table 1**)

Metabolism Regulating energy homeostasis, producing short-chain fatty acids and vitamins,

impacting glycemic control, interacting with incretins, regulating metabolism of

**Mechanism and target**

Immune system Influencing production of cytokines and antibodies

lipids and bone

Protection Killing or inhibiting unwanted organisms competing for nutrients

Gut microbiome can protect against pathogens by killing or inhibiting unwanted

organisms (e.g., *Clostridium difficile* genera) that are competing for nutrients.

Gut microbiome regulates immune system by influencing the production of

Gut microbiome is involved in several metabolic processes. These processes include regulation of energy homeostasis and body weight, production of shortchain fatty acids (following fermentation of nondigestible fibers) and vitamins (vitamins B, vitamin K) [32, 36], glycemic control [37, 38], interaction with incre-

Dysbiosis is observed in several medical conditions including obesity, malnutrition, type 2 diabetes, inflammatory bowel diseases, neurological disorders, and cancer [33, 42–48]. The dysbiosis can be the cause and/or the consequence of these

Gut microbiome influences drug pharmacokinetics and bioavailability, and thus,

Although there are some conflicting data, most studies have reported that in obesity, there is a lower gut microbiome diversity, a higher abundance of Firmicutes

affects the efficacy and safety of several drugs used to treat diseases [49].

**260**

diseases.

*Different tools used for gut microbiome manipulation in obesity management.*

#### *8.2.1 Diet*

Diet is an important factor for the manipulation of gut microbiome and management of obesity. The amount of daily caloric intake and the content of food significantly affect gut microbiome but with high interindividual variability [20, 21, 51]. A diet that is low in calories, low in fat (< 20% of total macronutrients), and high in fiber (≥ 30 g/day) has a favorable effect on gut microbiome (increase in richness, decrease in Firmicutes-to-Bacteroidetes phyla ratio) and weight control (weight loss).

#### *8.2.2 Prebiotics*

Prebiotics are chemicals (nondigestible food ingredients) inducing growth and/ or activity of bacteria [50, 52]. Prebiotics must be able to resist gastric acidity, resist enzymatic hydrolysis, resist absorption in the upper gastrointestinal tract, and be fermentable by the gut microbiome. Examples are inulin, lactulose, and resistant starch. Prebiotics can be found in many foods (e.g., leek, asparagus, onion, and soybean).

By modulating gut microbiome and lowering the production of lipopolysaccharide, prebiotics have the potential to manage obesity. In a double-blind, placebo-controlled clinical study, administration of oligofructose-enriched inulin (8 g/day) to overweight/obese children for 16 weeks caused a significant increase in *Bifidobacterium* (genus belonging to Actinobacteria phylum) and significantly slowed the body weight gain compared with placebo [53].

#### *8.2.3 Probiotics*

Probiotics are nonpathogenic living microorganisms with direct or indirect effect on gut microbiome [50, 54, 55]. Products containing probiotics should be tested for safety risks before marketing. Probiotics can be found in several foods (e.g., yogurt, cheese, and milk).

Probiotics can manage obesity by reducing the production of lipopolysaccharide through an impact on gut microbiome. In a double-blind, placebo-controlled clinical study, administration of fermented milk containing *Lactobacillus gasseri* species (LG2055) to overweight/obese adults for 12 weeks caused a significant decrease in body weight [56].
