**7. Discussion**

*Oral Health by Using Probiotic Products*

tine axis [27].

arises from findings found in animals (rats) [4].

diversity and microbial composition (**Figure 3**) [4].

weight loss and maintenance [27].

weight, and existing studies still show contradictory results; the available literature

However, several ways in which probiotics may influence adiposity and weight gain have been identified. These range from extracting calories from nutrients, generating specific metabolites, to modulating the behaviour of the brain-intes-

These hypotheses arise from research suggesting that obese individuals have a different composition of gut microbiota to subjects of a normal weight. For example, in people with obesity, they have observed a decrease in members of phylum *Bacteroidetes* (*Prevotella* and *Bacteroides* genera) and an increase in members of phylum *Firmicutes* (*Clostridium*, *Enterococcus*, *Lactobacillus*). It has been suggested that the aforementioned microorganisms have a greater capacity to extract energy from the undigestible waste products of nutrients that pass through the large intestine. These alterations are normalised with both phyla, when the subjects lose weight (increase of *Bacteroidetes* and decrease of *Firmicutes*) [29]. It has been observed that obese and inactive people have greater adiposity and insulin resistance but also less

A study conducted at Laval University in Canada evaluated the effect of *Lactobacillus rhamnosus* probiotic (LRP) supplementation on weight reduction, appetite control and eating behaviour in a group of obese men and women. The results showed that, in the group of women, the consumption of this microorganism provides beneficial effects on mood and behaviour linked to dietary intake, compared to the group of men and those who received the placebo. This opens up a series of possibilities for health professionals with regard to the implementation of successful obesity programmes, especially considering that many individuals experience great difficulties when trying to sustain their weight loss. This is mainly due to poor appetite control and not taking the necessary action to lead a healthy lifestyle. Based on the findings of this research, it has been suggested that some probiotic strains could be included as environmental factors with regard to body

Corroborating these findings, a multicentre, randomised, double-blind study conducted on 29 men and 14 women, using the microorganism *Lactobacillus gasseri* and administered through a probiotic yogurt for 12 weeks, demonstrated, in the individuals analysed, a 4.6% decrease in areas of abdominal and subcutaneous fat,

Nevertheless, and contrary to these results, several investigations using a similar model maintain that administering yogurt with other species of probiotics such as

as well as a decrease in BMI, waist and hip circumference [4].

*Gut microbiota imbalance between healthy and obese individuals.*

**100**

**Figure 3.**

Currently, obesity is a major public health problem worldwide. There is no specific cause that determines the development of this disease; on the contrary, it is the result of numerous factors that interact, including genetic, environmental, food, lifestyles, etc. [27]; however, the study of intestinal microbiota and its implication in obesity has aroused curiosity among scientists. The current information obtained comes mainly from the work done in rats and, exceptionally, in humans [17].

Although much of the research indicates that there are differences in the composition of the intestinal microbiota of obese and normal subjects, there is still controversy about it [4].

As indicated in this chapter, the development of these intestinal bacterial communities depends to a large extent on the host and can be modified by exogenous and endogenous influences. Ghosh et al. in 2011 talked about the direct relationship between food patterns and the microbiota composition [18].

In 2013, Devaraj et al. established the existing association in the imbalance of the microbiota where the composition of this is affected producing an increase of the *Firmicutes* genus and a decrease of the *Bacteroidetes*; this instability would affect the metabolism of the human being and as a consequence the appearance of various metabolic diseases among which obesity stands out [21]. In the same way, several publications continue confirming this situation, for example, the study of Jameel Barkat of the year 2018 relates the role of the microbiota in the regulation of energy balance, food absorption and its relationship with the appearance of various diseases: diabetes, metabolic syndrome and obesity, among others [30]. A study was conducted in 36 adults analysing the faecal bacterial composition, finding a decrease in *Firmicutes* and *Clostridia* in diabetic patients compared to the control group. This same research reaffirms that among the factors that alter the stability

and composition of the microbiota are the changes in the diet (high-fat diets) that impact on the relationship between *Firmicutes* and *Bacteroidetes* [31].

In order to demonstrate the aforementioned, it is convenient to point out two investigations carried out in 2015; Kasai et al. [32] conducted a study in Japanese population where they observed that bacterial diversity was significantly higher in obese subjects than in nonobese subjects. In the first group, there was a decrease of the *Bacteroidetes* species and increase of *Firmicutes* [31]. Angelakis et al. showed in a study performed in thin and obese subjects that the *Firmicutes* and *Actinobacteria* genera were the most predominant of the duodenal microbiota; however, in subjects with obesity, a higher proportion of anaerobic and lower proportions of aerobic genus were observed [33].

On the other hand, there are other authors such as Murugesan et al. that indicate in a study carried out in 190 Mexican children between 9 and 11 years old no significant differences between the different bacterial species of microbiota in the different evaluated subjects [34]. The same happens in Hu et al. In 2015, when 134 Korean adolescents from 13 to 16 years old were evaluated, no significant differences were found between the *Bacteroidetes*, *Firmicutes* and *Proteobacteria* populations [35].

It is widely recognised in the scientific community that diets with high-fat content favour the development of resistance to leptin, hyperphagia and therefore obesity. A study points out that the inclusion in the diet of the oligofructose prebiotic prevents the development of resistance to leptin and hyperphagia in rats; from this it is concluded that oligofructose reduces the energy of ingestion, and therefore it is suggested that it has the potential for the obesity treatment [36].

On the other hand, the use of probiotics is associated with multiple health benefits, which are highly endorsed by the scientific community. So far, the data that associate a specific type of microorganisms with human obesity are not conclusive, since they do not say whether it is the microbiota that plays a cause-effect function of obesity or whether it is the intestinal microbiota that is modulated in response to obesogenic diets and other factors related to the pathogenesis of this condition [28–30, 37].

Studies aimed at modulating the gut microbiota to prevent or control the obesity of the host, including the use of probiotics, show positive results [25, 30].

With the reviewed bibliographic evidence, it is crucial to highlight the importance of including the gut microbiota as one of the factors involved in the management of obesity; however, more conclusive information must be analysed about it evaluating what happens even in other specific groups such as the child population.
