Probiotics, prebiotics, energy balance and obesity: mechanistic insights and therapeutic implications.

Obesity-related disorders are related to energy homeostasis and inflammation; gut microbiota are involved in several host metabolic functions and may play an important role in this context through several mechanisms: increased energy harvest from the diet, regulation of host metabolism, and modulation of inflammation. Human gut flora comprises bacteria belonging to 3 bacterial phyla: the gram-positive Firmicutes and Actinobacteria and the gram-negative Bacteroidetes. Firmicutes is the largest bacterial phylum and comprises more than 200 genera, including Lactobacillus, Mycoplasma, Bacillus, and Clostridium species. Although each subject has a specific gut microbiota, a core human gut microbiome is shared among family members despite different environments; nevertheless, the microbiome dynamically changes in response to some factors, including dietary nutrients, illness, and antibiotic use. This review discusses the interaction of gut microbiota with host metabolism and the impact of manipulating microbiota composition on the pathogenesis and the treatment of obesity.