**7.1 Diet**

As mentioned previously, nutritional recommendations for a Mediterranean diet or plant-based diet, which are rich in polyunsaturated and monounsaturated fat, have

**Figure 4.**

*Different level interventions for gut microbiota modulation.*

*Gut Microbiota and Bariatric Surgery DOI: http://dx.doi.org/10.5772/intechopen.107175*

been associated with higher bacterial diversity, higher levels of total SCFA [64, 65], and significant reductions in plasma cholesterol [66]. Increased physical activity has also demonstrated beneficial changes to the gut microbiome [67]. To establish a clear intervention effect on the gut microbiome through modulation of dietary fat, both in quantity and quality, more clinical trials are needed to establish nutritional recommendations [68].

#### **7.2 The "biotics": Prebiotics, probiotics, symbiotics, and postbiotics**

Complex mixtures of bacterial strains (probiotics) and various fiber dosages (prebiotics), which are "symbiotic", have been used in multiple studies regarding obesity treatment. *In vitro* studies have shown that symbiotics are more efficient at modulating gut microbiota than prebiotics or probiotics alone [69].

According to the consensus statement of the International Scientific Association of Probiotics and Prebiotics (ISAPP), postbiotics are defined as "preparations of inanimate microorganisms and/or their components that confer a health benefit on the host" [70]. SCFAs are currently the most common type of postbiotics used. These compounds increase brown adipose tissue and promote browning of white adipose tissue, as well as regulate appetite by interfering with the gut-brain axis [71]. Overall, probiotics, prebiotics, symbiotics, and postbiotics appear to exhibit beneficial effects on gut microbiota modulation. Nevertheless, further large-scale trials are required to evaluate their beneficial properties, safety profile, dosage, and the durability of their beneficial effects in the prevention and treatment of obesity [72].

#### **7.3 Fecal microbiota transplantation (FMT)**

FMT is a modulation strategy that transfers a complete microbial ecosystem from a healthy donor to a patient with the aim of ecologically restoring an aberrant microbiota [73]. The donor's microbiota can be administered through colonoscopy or orally by capsules. This technique has been widely investigated for the treatment of recurrent *Clostridioides difficile* infection, with outstanding therapeutic success rates; however, there is no current indication for obesity [74].

Although several studies have been performed in patients with various inflammatory disorders, such as irritable bowel syndrome and obesity-associated metabolic disorders, therapeutic success rates were not as high, or no effect was observed [75–77].

Further studies are required to understand the mechanisms through which changes in gut microbial ecology and engraftment of microbiota affect metabolic outcomes for patients with obesity. In addition, further research is needed to better define the optimal fecal microbial preparation as well as dosing and method of delivery [78].
