Beyond Calories: How the Gut Microbiome Is Rewriting the Obesity Story

Dr Sanjay Kalra, Treasurer, International Society of Endocrinology (ISE), Vice President, South Asian Obesity Forum (SOF), Bharti Hospital, Karnal, INDIA

Obesity is increasingly being understood as a gut microbiome–driven metabolic disorder, opening the door to more personalized and effective treatment strategies.

Obesity is no longer a distant public health concern—it is a present and growing global reality. With over 2.6 billion people currently living with overweight or obesity and projections crossing 4 billion by 2035, traditional explanations centred only on calories and inactivity are no longer sufficient. Increasingly, science is pointing us inward—towards the gut microbiome.

The gut microbiome, a vast ecosystem of microorganisms, plays a decisive role in regulating metabolism, energy balance, inflammation, and appetite. In individuals with obesity, this ecosystem is often disrupted, marked by reduced microbial diversity and shifts in key bacterial populations. These changes influence how efficiently energy is harvested from food, how fats are stored, how insulin responds, and how inflammation is triggered—quietly shaping long-term metabolic health.

Diet emerges as a powerful modulator of this microbial world. Fiber-rich, plant-based eating patterns nurture beneficial microbes and their metabolites, while highly processed, high-fat diets promote dysbiosis. Encouragingly, emerging microbiome-based strategies—such as targeted probiotics, prebiotics, and personalized nutrition—offer new hope where one-size-fits-all approaches have fallen short.

Understanding obesity through the lens of the gut reframes it as a complex, biologically driven condition rather than a simple failure of willpower. As research advances, integrating microbiome-focused strategies into clinical practice may redefine how we prevent and manage obesity—making care more precise, humane, and effective.

(Source: Borrego-Ruiz A, Borrego JJ. The Gut Microbiome in Human Obesity: A Comprehensive Review. Biomedicines. 2025 Sep 5;13(9):2173.)