**3. Gut microbes in connection with obesity**

The idea for studying obese people's gut microorganisms came from the idea that gut flora might be a vital component of their long-term health. The earliest evidence of a link between gut flora and obesity was discovered in germless mouse studies. The quantity of fat and insulin sensitivity inside the transplanted increased even when food consumption was reduced, showing that gut microbes may help the recipient in the formation of adipose tissue [87]. Its Firmicutes ratio rose sharply in fat mice [88], showing that the obese mice's microbiome was good at taking energy from the feed. Systems can be seen in individuals; for instance, in the guts of obese children, their ratio of Firmicutes climbed whereas the quantity of Bacteroidetes decreased [89]. The Firmicutes/Bacteroidetes ratio increased as BMI increased, according to a study of the Ukrainian population [90].

In overweight and obese people, supplementing with *A. muciniphila* improves metabolic indices [91]. Traditional probiotics like Lactobacillus and Bifidobacterium, for example, help to maintain healthy gut flora. Crovesy et al. [92] investigated the impact of Bacteria on obesity rates but found that its beneficial benefits were genus. The frequency of *Lactobacillus paracasei* was shown to be interrelated to fat, but the number of Escherichia repeating unit and *Lactobacillus acidophilus* gasseri was shown to be favorably related to obesity. Animal studies have shown that Bifidobacterium can help people lose weight. Bifidobacterium demonstrated a strain-dependent impact on obesity in diet-induced obesity animal models [93]. Obesity is linked to a reduction in Bifidobacterium abundance in the intestine [94]. The study on intestinal flora and obesity is represented in **Table 1**.


#### **Table 1.**

*Linkage of obesity with gut microbiomes.*

#### **3.1 Obesogenic gut microbiota**

Firmicutes and Bacteroidetes, for particular, have been identified as obesitypromoting intestinal flora, which can lead to the growth of obese [97].

#### **3.2 Firmicutes and Bacteroidetes**

Ruminiococcus, Candida, and Lactobacillus have been the most prevalent representatives of the phylum Firmicutes phylum Bacteroidetes in the gut bacteria, accounting for 90% of types of bacteria [44, 98]. Regulating glucagonlike peptide 1 release may aid to alleviate insulin sensitivity and obesity in way of eating obese C57BL/6 J mice given antibiotics [99]. Inside the intestines of adult C57BL/6 J rats fed a strong diet, firmicutes were found mainly [100]. In obese people and obese mice, a great proportion of Firmicutes to Bacteroidetes has just been reported as an adiposity trait of the gut microbiome [42]. Obese women having elevated toll-like receptor 5 gene expression were also shown to have a greater number of the genus [101]. Egyptian researchers examined the gut microbiome of 51 obese persons (23 kids and 28 individuals) to the gut microbiome of 28 healthy individuals in a study. In a survey of 17 children and 11 adults, researchers observed that the phyla Firmicutes and Bacteroidetes were significantly higher in the obese group (p 0.001, p = 0.003) [102]. Lactobacillus has been divided into various subgroups, each of which has been associated with obesity and the genesis of obesity. A variety of key enzymes are missing in bacteria that promote weight gain, including sugar enzymes, antioxidants, and dextrin, L-rhamnose, or acetate synthetases [103].

The three principal Bacteroidetes taxa present in the human stomach are Bacteroides, Prevotella, and Porphyromonas. Bacteroides account for more than a third of all gut bacteria, and it's particularly prevalent in Westerners who consume a high-fat or high-sugar diet [104]. Together in a controlled trial with 138 babies aged 3 years, the utilization of Bacteroides in the intestines was found to be positively associated with bodyweight [105]. Bifidobacteria and Lactobacillus species have also been linked to weight increase in children [106, 107].
