What Is Obesity? 

Obesity is a chronic disease¹ defined as a body mass index (BMI) greater than 30 kg/m². It is a multifactorial disease characterized by excessive accumulation of adipose (ie, fat) tissue.² Body weight, energy intake, and energy expenditure – crucial factors of obesity – are influenced and regulated by various factors such as hormonal, metabolic, and neuronal mechanisms as well as environmental and internal factors.³ Recent research suggests that the human gut microbiota can also play a significant role, affecting metabolic processes as well as the development of obesity.

What Is Gut Microbiota?

The gut microbiota is a complex ecosystem comprising of microorganisms.^3,4 It is thought that around 10¹⁴ bacterial cells from 100-200 strains populate the gut, with each section of the digestive system varying in the amount and composition of bacteria.⁴ The gut microbiota has a synergistic relationship with the human host, meaning that while it derives nutrients and energy from the human diet, it also protects the human gut from harmful pathogens and aids with digestion and absorption of nutrients.   

How Is Gut Microbiota and Obesity Related?

Recent research has suggested that the gut microbiota plays an important role in obesity and its related comorbidities.⁴ Studies show that the gut microbiota can affect adiposity and glucose metabolism and that the composition of gut microbiota differ between individuals with obesity and those with normal weight. It has been shown that the gut microbiota in individuals with obesity tend to be more abundant in strains of bacteria that more readily harvest energy from the diet, when compared to microbiota in individuals with normal weight. For instance, Bacteriodes are consistently found more abundantly in lean individuals whereas Firmicutes are found more abundantly in those with obesity and disrupted microbiota. Additionally, individuals who consume different types of diet, such as the vegetarian diet vs. omnivorous diet, also have markedly different microbiota populating the gut, showing that diet has a significant influence on the health and balance of gut microbiota.

How Can You Promote Healthy Gut Microbiota?

Given the relationship between gut microbiota and obesity, new therapeutic approaches are emerging to promote healthy gut microbiota to ultimately improve metabolic health.⁴ Changes to diet, additions of probiotics and prebiotics as supplements, and fecal microbiota transplant are some potential ways to improve gut health. Research shows that diet-induced weight loss was associated with increased richness in the genes of gut bacteria and may lower chronic systemic inflammation, showing that healthy diet can promote gut health. Probiotics may also help regulate gut microbiota and have some metabolic benefits such as alleviating insulin resistance. Fecal microbiota transplant, however, is promising but has not yet shown clear results on improving obesity and metabolic conditions in individuals with obesity, and more research is needed to study its long-term benefits.³