Gut-microbiota (GM) is considered a hidden metabolic organ of the human body, providing biochemical pathways which are absent in the host. Balanced diet with calorie restriction (CR) promotes growth of healthy microbiota, leading to longevity by down-regulating inflammatory responses. While, dysbiosis leads to body dysfunction, inducing metabolic disorders, causing poor epithelial architecture, and impeding the development of mucosal-associated lymphoid tissue, resulting in with reduced T and B cell populations, rendering the body prone to infections, cancer and allergy. The GM enzymes activity is a new risk factor for cancer while gut-derived interleukin-6 is associated with hepatocellular carcinoma development. GM can also influence the brain biochemistry and emotional behavior. The altered GM affects the genes involved in second messenger pathway and long-term potentiation, leading to their differential expression in the hippocampus, cortex, striatum and cerebellum. In addition, the dysbiotic GM is associated with autistic disorder. Living with dysbiotic GM is possible with consequences of serious impairments.