The gut microbiota in obesity and weight management: microbes as friends or foe?

This Review outlines evidence that the gut microbiota is involved in regulating body weight homeostasis. In addition, the opportunities, limitations and challenges of using gut microbiota-related approaches as a means to achieve and maintain a healthy body weight in people with overweight or obesity are discussed. Obesity is caused by a long-term difference between energy intake and expenditure - an imbalance that is seemingly easily restored by increasing exercise and reducing caloric consumption. However, as simple as this solution appears, for many people, losing excess weight is difficult to achieve and even more difficult to maintain. The reason for this difficulty is that energy intake and expenditure, and by extension body weight, are regulated through complex hormonal, neural and metabolic mechanisms that are under the influence of many environmental factors and internal responses. Adding to this complexity, the microorganisms (microbes) that comprise the gut microbiota exert direct effects on the digestion, absorption and metabolism of food. Furthermore, the gut microbiota exerts a miscellany of protective, structural and metabolic effects both on the intestinal milieu and peripheral tissues, thus affecting body weight by modulating metabolism, appetite, bile acid metabolism, and the hormonal and immune systems. In this Review, we outline historical and recent advances in understanding how the gut microbiota is involved in regulating body weight homeostasis. We also discuss the opportunities, limitations and challenges of using gut microbiota-related approaches as a means to achieve and maintain a healthy body weight.

Automated summary

This Review summarizes the evidence that the gut microbiota plays a role in regulating body weight homeostasis. It discusses the opportunities, limitations, and challenges of using gut microbiota-related approaches to achieve and maintain a healthy body weight in overweight or obese individuals. The complex hormonal, neural, and metabolic mechanisms that regulate energy intake and expenditure, and therefore body weight, are influenced by environmental factors and internal responses. Additionally, the microorganisms in the gut microbiota have direct effects on food digestion, absorption, and metabolism, as well as various protective, structural, and metabolic effects on the intestines and peripheral tissues, which further impact body weight. This Review outlines the historical and recent advances in understanding the involvement of the gut microbiota in regulating body weight homeostasis and discusses the opportunities, limitations, and challenges of using gut microbiota-related approaches for maintaining a healthy body weight.