This review provides an updated overview of the current understanding of the gut microbiota and its role in various diseases, including metabolic syndrome, obesity-related diseases, liver disease, inflammatory bowel disease (IBD), and colorectal cancer (CRC). The gut microbiota, often referred to as a new organ or immune system, has been shown to influence host health and disease through complex interactions. Recent advancements in 'omic' technologies have facilitated large-scale analysis of the microbial community, revealing its significant impact on host physiology. The review discusses the potential of manipulating the gut microbiota through various strategies such as antibiotics, probiotics, prebiotics, polyphenols, and fecal microbiota transplantation (FMT). It highlights the importance of dietary modulation, particularly in maintaining carbohydrate fermentation, which is crucial for gut health. The review also explores the link between the gut microbiota and obesity-related diseases, liver diseases, IBD, and CRC, emphasizing the need for further research to understand the mechanisms and develop targeted therapies. The authors conclude by emphasizing the potential of personalized healthcare approaches that integrate the gut microbiota into disease prevention and treatment.This review provides an updated overview of the current understanding of the gut microbiota and its role in various diseases, including metabolic syndrome, obesity-related diseases, liver disease, inflammatory bowel disease (IBD), and colorectal cancer (CRC). The gut microbiota, often referred to as a new organ or immune system, has been shown to influence host health and disease through complex interactions. Recent advancements in 'omic' technologies have facilitated large-scale analysis of the microbial community, revealing its significant impact on host physiology. The review discusses the potential of manipulating the gut microbiota through various strategies such as antibiotics, probiotics, prebiotics, polyphenols, and fecal microbiota transplantation (FMT). It highlights the importance of dietary modulation, particularly in maintaining carbohydrate fermentation, which is crucial for gut health. The review also explores the link between the gut microbiota and obesity-related diseases, liver diseases, IBD, and CRC, emphasizing the need for further research to understand the mechanisms and develop targeted therapies. The authors conclude by emphasizing the potential of personalized healthcare approaches that integrate the gut microbiota into disease prevention and treatment.