**5.2 Obesity**

Many recent meta-analysis studies proved that probiotics significantly had a promising effect on weight loss and body mass index (BMI) improvement [119–122]. Besides, in one study, it was shown that when the combination of different probiotic strains was used for more than 8 weeks, reducing the body weight and BMI happened [123]. However, some other meta-analysis studies did not approve this statement [124, 125]. Furthermore, in another research was done by million and colleagues reported different species of *Lactobacillus* have different effects on weight in both humans and animals [126]. According to this research probiotic strains associated with weight gain in animals were *Lactobacillus fermentum* and *Lactobacillus ingluviei*.

And a probiotic strain with anti-obesity effect was *Lactobacillus plantarum*, in addition, *Lactobacillus gasseri* was an effective strain for weight loss in both humans and animals [126]. Contradictory results on the effect of probiotics in weight modifications may be due to differences in the probiotic strains and host.

The gut microbiota effects on energy regulation can be a prime factor in the development of obesity [127, 128]. Human intestinal microbiota is a complicated ecosystem that includes numerous kinds of microorganisms like bacteria, viruses, archaea, fungi, protists, nematodes, and phages, involved in various functions of host metabolism [129]. A higher proportion in the strains of *Bacteroides fragilis*, *Clostridium leptum*, and *Bifidobacterium catenulatum* and a lower percentage of *Clostridium coccoides*, *Lactobacillus sensu lato*, and *Bifidobacterium* display considerable weight loss [130, 131], therefore, probiotics may be a powerful tool in modulating obesity by changing the gut microbiota composition [132, 133].

The gut microbiota remarkedly can ferment the indigestible carbohydrates into short-chain fatty acids (SCFAs). SCFAs are the main metabolites of intestinal microbiota which have an important role in energy, glucose, lipid homeostasis and intestinal health [134, 135]. The most plentiful SCFAs are acetate, butyrate, and propionate (encompass 95% of all SCFAs), which are the main substrates for glucose metabolism [129]. Multiple animal studies have shown that the gut microbiota and their metabolites, especially SCFAs, have a significant role in obesity [136–138] and also in the prevention and treatment of obesity-associated insulin resistance [139–142]. Therefore, it is recommended that SCFAs have the ability to control host energy metabolism in the advancement of diet-induced weight and also can be applied for de-novo synthesis of lipid and glucose [143]. However, in human studies, there is contradiction in the association between SCFAs and obesity. For instance, some studies have demonstrated a positive interaction between fecal SCFAs levels [144–146] and obesity while others reported an unfavorable result [147]. Evidence shows that acetate plays an important role in the hypothalamic control of appetite [139] and also increase anorexigenic neuropeptide expression [139] so it is suggested that acetate may be a functional treatment for obesity. Among acetate-producing probiotic strains we can suggest *Methanobrevibacter smithii* and *Blautia hydrogenotrophica* [148]*.* Chambers et al. have demonstrated that colonic propionate can acutely lessen energy intake and prevent long-term weight gain in people [149]. Considering probiotics, the species of genera *Lactobacillus* and *Bifidobacterium* basically create butyrate and propionate [150]. Butyrate has the ability to alleviate obesity and other metabolic complications which are very usual in western nations [151]. For presentation, a decrease in the number of microbes that produce butyrate in humans is connected with an elevated threat of metabolic disease [152]. *Clostridium butyricum, Faecalibacterium prausnitzii*, *Eubacterium rectale*, *Roseburia* are some of probiotic strains found in the intestines of healthy animals and humans which produce butyrate [153, 154].

### **5.3 Other metabolic disorders**

Meta-analysis studies reporting the effectiveness of probiotic supplementation on lipid and glucose metabolism on pregnant women [155] and patients with diabetes [156]. And also, the result of another meta-analysis study suggests that probiotics should be used as a new way to control and management of lipid profile and blood pressure in type 2 diabetic patients [157]. Probiotics play their role in reducing serum cholesterol (hypocholesterolemia) through some mechanisms including binding cholesterol and fatty acids to the probiotic bacteria's cellular membrane [147],

### *Probiotic Effects on Disease Prevention and Treatment DOI: http://dx.doi.org/10.5772/intechopen.109717*

deconjugation of bile acids by the presence of bile salts hydrolase enzymes in lactic acid bacteria [139, 148–150], the transformation of cholesterol to coprostanol and excreted into feces [147]. A clinical trial of 84 pregnant women with gestational diabetes mellitus (GDM) receiving 300 mg/day of yogurt contained two probiotic strains including *Lactobacillus acidophilus* and *Bifidobacterium lactis* or placebo (ordinary yogurt) for 2 months reported that consumption of yogurt probiotics can manage blood glucose better and also the rate of macrosomia might be reduced in pregnant women by GDM through this regimen [158].
