Gut Microbiome in Obesity Management

*Hassan M. Heshmati*

#### **Abstract**

Obesity is a worldwide pandemic causing increased morbidity/mortality and high cost for the society. Management of obesity requires multidisciplinary approaches including diet, food supplement, exercise, behavior change, drug, medical device, gut microbiome manipulation, and surgery. Over the past two decades, there has been a growing awareness of the importance of gut microbiome in human health and disease. Profound changes affecting the diversity and the abundance of gut microbiome are associated with several disorders including obesity. A decrease in microbiome diversity and an increase in the ratio of Firmicutesto-Bacteroidetes phyla have been reported in obese subjects. The gut microbiome can be manipulated to change the host metabolism and manage obesity. Potential interventions include diet (e.g., low calories, low fat, and high fiber), prebiotics (e.g., inulin, lactulose, and resistant starch), probiotics (e.g., yogurt, cheese, and milk), synbiotics (combination of prebiotics and probiotics), bariatric surgery (e.g., Roux-en-Y gastric bypass), and fecal microbiota transplantation (through colonoscopy, esophagogastroduodenoscopy, orogastric tube, or oral capsule). A better understanding of the interactions between different diets and gut microbiome should help the development of new guidelines for the prevention and management of obesity.

**Keywords:** gut microbiome, obesity, weight management

#### **1. Introduction**

Obesity is excess body weight for a given height, defined by a body mass index (BMI) ≥ 30 kg/m<sup>2</sup> . In some Asian countries (e.g., Japan), the threshold to define obesity is 25 kg/m<sup>2</sup> . The main cause of obesity is an imbalance between energy intake and energy expenditure. Obesity is a worldwide pandemic associated with increased morbidity/mortality and high cost for the society. The prevalence of obesity is increasing exponentially. The number of adult subjects with obesity is around 700 million worldwide. Near 4 million subjects die each year from the consequences of obesity. The annual cost of obesity is more than \$2 trillion [1–3].

Management of obesity requires multidisciplinary approaches including diet, food supplement, exercise, behavior change, drug, medical device, gut microbiome manipulation, and surgery [1, 4–9]. The annual obesity treatment market is around \$6 billion.

The human intestine harbors a complex and diverse microbial ecosystem referred to as gut microbiome [10–14]. This rich community of microorganisms has co-evolved in a symbiotic relationship with humans. Its diversity is influenced by several factors including host genetics, mode of birth, age, gender, pregnancy, BMI, diet, medications, and surgery [12, 15–31]. The understanding of the gut microbiome evolves at a rapid pace, but the practical application of this knowledge is still in its infancy. The gut microbiome is essential for the maintenance of human health. It is involved in protection against pathogens and regulation of immune system and metabolism [32]. Profound changes affecting the diversity and the abundance of gut microbiome (dysbiosis) are associated with several disorders including obesity [33]. The prevention and management of obesity may benefit from manipulation of gut microbiome.
