The gut-brain-fat axis: How your microbes influence your metabolism

Trillions of tiny microbes live in your gut. They help manage hunger, inflammation, and how your body stores fat. Doctors now see them as a key part of understanding weight and health. This group of bacteria, known as the gut microbiota, is active and important.

Research shows that people with obesity often have different gut bacteria profiles compared to the lean ones. “The balance between two types of gut bacteria; Firmicutes and Bacteroidetes, can tell a lot about your health,” says Dr Muffazal Lakdawala, Director of Surgery at Reliance Foundation Hospital. “A higher proportion of Firmicutes tends to increase energy extraction from food, which may contribute to weight gain,” he adds.

These microbes ferment dietary fibres, producing short-chain fatty acids (SCFAs) such as butyrate and propionate that not only reduce inflammation but also improve insulin sensitivity and help regulate appetite by signalling the brain.

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However, when the gut’s microbial balance is disrupted, a state called dysbiosis, harmful bacteria, may release substances like lipopolysaccharides (LPS) that cause inflammation in the body. This triggers insulin resistance, encourages fat storage, and disturbs the brain’s hunger cues.

• It's a two-way street: Dr Lakdawala adds, "Factors like chronic stress, poor diet, and lack of sleep can negatively affect gut microbes, which in turn worsen metabolic health.” However, interventions such as prebiotics, probiotics, and fermented foods can restore a healthier microbial environment and improve key metabolic markers like triglycerides and uric acid.

• Your gut microbes directly impact energy balance: The microbes in your gut influence how many calories you absorb from food. A microbial community skewed towards Firmicutes may extract more energy, increasing fat storage risk.

• Short-chain fatty acids are metabolic superheroes: SCFAs produced by gut bacteria reduce inflammation, improve insulin sensitivity, and send signals to the brain to help control appetite and energy use.

• Dysbiosis fuels inflammation and metabolic disruption: An imbalance in gut bacteria can cause systemic inflammation, insulin resistance, and faulty hunger signals, all contributing to weight gain and metabolic diseases.

• Lifestyle factors affect your gut health: Chronic stress, processed foods, and poor sleep harm your gut microbiota, exacerbating metabolic problems.

• Nurture your gut microbes with diet: Prebiotics (fibres feeding good bacteria), probiotics (live beneficial bacteria), and fermented foods can restore balance and support healthier metabolism.

• Gut health and weight-loss strategies: “Addressing gut health alongside diet and exercise leads to better metabolic improvements. It’s about supporting the microbial ecosystem, not just counting calories,” says Dr Lakdawala.