The review discusses the impact of diet and lifestyle on gut microbiota and human health. It highlights the role of diet in shaping the composition and activity of gut microbes, which in turn can influence health. Molecular technologies have advanced our understanding of gut microbial diversity and complexity. Diet, particularly macronutrients, plays a major role in shaping these populations. While the effects of carbohydrates on gut microbiota are well understood, the impacts of dietary fats and protein are less clear. Both short- and long-term dietary changes can influence microbial profiles, and infant nutrition may have lifelong consequences through immune system modulation. Environmental factors, including lifestyle, also impact the microbiota, though this area is poorly understood. The review discusses the use of prebiotics and probiotics to modify microbial populations and outlines areas for future research. The gut microbiota is composed of numerous microorganisms, including bacteria, yeasts, viruses, and parasites. The composition and function of these microbes vary along the gastrointestinal tract, with the majority found in the large bowel. Gut microbes produce various products that can influence health, including vitamins, secondary bile acids, and lipopolysaccharides. Some of these products are beneficial, while others can be toxic. The gut microbiota also plays a role in immune function and the maintenance of a healthy gut barrier. Dietary fiber is particularly important for maintaining a healthy gut microbiota, as it promotes the growth of beneficial bacteria and helps maintain gut health. Lifestyle factors such as smoking, lack of exercise, and stress can significantly impact the gut microbiota. Obesity is associated with changes in gut microbial populations, with increases in Firmicutes and decreases in Bacteroidetes. These changes may contribute to adiposity through increased energy harvest. The gut microbiota is also influenced by geography, with differences in microbial composition observed between populations in different regions. The review also discusses the impact of polyphenols on the gut microbiota and the effects of Western-style diets on gut health. These diets are associated with chronic diseases such as cardiovascular disease, colorectal cancer, and type II diabetes. The review highlights the importance of understanding the interactions between diet, lifestyle, and gut microbiota to improve human health. It also discusses the potential benefits of probiotics and prebiotics in modifying microbial populations and improving health outcomes. Despite advances in understanding the gut microbiota, there are still many gaps in knowledge that require further research.The review discusses the impact of diet and lifestyle on gut microbiota and human health. It highlights the role of diet in shaping the composition and activity of gut microbes, which in turn can influence health. Molecular technologies have advanced our understanding of gut microbial diversity and complexity. Diet, particularly macronutrients, plays a major role in shaping these populations. While the effects of carbohydrates on gut microbiota are well understood, the impacts of dietary fats and protein are less clear. Both short- and long-term dietary changes can influence microbial profiles, and infant nutrition may have lifelong consequences through immune system modulation. Environmental factors, including lifestyle, also impact the microbiota, though this area is poorly understood. The review discusses the use of prebiotics and probiotics to modify microbial populations and outlines areas for future research. The gut microbiota is composed of numerous microorganisms, including bacteria, yeasts, viruses, and parasites. The composition and function of these microbes vary along the gastrointestinal tract, with the majority found in the large bowel. Gut microbes produce various products that can influence health, including vitamins, secondary bile acids, and lipopolysaccharides. Some of these products are beneficial, while others can be toxic. The gut microbiota also plays a role in immune function and the maintenance of a healthy gut barrier. Dietary fiber is particularly important for maintaining a healthy gut microbiota, as it promotes the growth of beneficial bacteria and helps maintain gut health. Lifestyle factors such as smoking, lack of exercise, and stress can significantly impact the gut microbiota. Obesity is associated with changes in gut microbial populations, with increases in Firmicutes and decreases in Bacteroidetes. These changes may contribute to adiposity through increased energy harvest. The gut microbiota is also influenced by geography, with differences in microbial composition observed between populations in different regions. The review also discusses the impact of polyphenols on the gut microbiota and the effects of Western-style diets on gut health. These diets are associated with chronic diseases such as cardiovascular disease, colorectal cancer, and type II diabetes. The review highlights the importance of understanding the interactions between diet, lifestyle, and gut microbiota to improve human health. It also discusses the potential benefits of probiotics and prebiotics in modifying microbial populations and improving health outcomes. Despite advances in understanding the gut microbiota, there are still many gaps in knowledge that require further research.