The majority of weight conversations are about calories, exercise, and willpower. Clinical practice tells a wider story. "Two people can eat similar diets and do similar things and have very different results. One loses pounds gradually and the other struggles with pounds for all it is worth. Some of the difference begins in the gut.

The digestive system does much more than just process food. It constantly communicates with the brain, liver, pancreas and immune system. It impacts hunger, satiety, blood sugar control, fat storage and energy utilization. When these signals remain balanced, it's easier to keep a healthy weight. When they're disrupted, appetite changes, metabolism slows, fat storage goes up, and blood sugar gets harder to control.

The Gut is a Metabolic Control Centre

Trillions of bacteria, fungi and other microorganisms, together called the gut microbiome, live in the intestine. These microorganisms aid in digestion, produce vital nutrients, control inflammation, and affect metabolism.

Research has shown over and over that gut microbiome diversity tends to be lower among people living with obesity than among people at a healthy weight. Some bacterial populations extract more calories from the same meal, so the body can absorb more energy without increasing food intake.

The microbiome also produces short chain fatty acids from fibre in the diet. These compounds affect the functioning of the liver, insulin sensitivity and the metabolism of fats. It helps normal metabolism with a healthy balance. An unhealthy balance encourages more fat storage and chronic low-grade inflammation.

This also helps to explain why two people eating similar meals can respond differently over the course of several months.

Hunger Starts in the Gut Before It Reaches the Brain

Appetite is controlled by a complex system of hormones, many of which are produced in the digestive tract.

GLP-1 and peptide YY signal satiety after eating, while ghrelin stimulates hunger before meals. This hormonal conversation is controlled by healthy gut bacteria.

When the microbiome goes awry from diets loaded with refined carbs, sugary drinks, ultra-processed foods, and not enough fibre, these signals become skewed. Hunger returns sooner and fullness later. And snacking is often more frequent.

Food choices are shaped by biology as much as by behaviour. Seeing this relationship in this way changes the way obesity is understood and treated.

The Gut Also Affects Blood Sugar

The hormonal pathways that affect appetite also influence insulin production and blood sugar regulation.

Changes in the intestinal barrier allow bacterial toxins, notably lipopolysaccharides, to enter the circulation. This results in ongoing inflammation all over the body. Over time, inflammation decreases insulin sensitivity, making it harder to control blood sugar.

This relationship explains why obesity and type 2 diabetes are often seen in tandem.

One in three Indian adults has abdominal obesity, one in four has generalised obesity and one in five has elevated cholesterol, according to a report in The Lancet Diabetes & Endocrinology (2023) by the Indian Council of Medical Research. Many times, these conditions have the same metabolic pathways.

Belly Fat Is an Indicator of What's Going on Inside Your Body

Body weight by itself rarely tells the whole story. Fat stored around the abdomen is very different from fat stored under the skin.

Visceral fat is the fat that surrounds your liver, pancreas, and intestines. It actively spews inflammatory chemicals that disrupt the action of insulin and increase the risk of type 2 diabetes, fatty liver disease, hypertension, heart disease and several cancers.

Subcutaneous fat, which lies just under the skin on the hips, thighs and arms, has a lower relative metabolic risk.

This explains why people with similar BMIs can have very different health profiles. Waist circumference and abdominal fat are often more telling of metabolic health than body weight alone.

Daily Habits Shape Microbiome

The gut microbiome is constantly changing in response to our daily habits.

A diet rich in fibre from vegetables, fruits, legumes, whole grains, nuts and fermented foods supports the growth of beneficial bacteria. Regular physical activity increases microbial diversity and improves insulin sensitivity. Getting enough sleep helps regulate appetite hormones, and managing stress supports healthy communication between the gut and brain.

The inverse pattern gradually destroys metabolic health. Diets high in ultra-processed foods, extra sugar, erratic meal times, physical inactivity, poor sleep and chronic stress all deplete microbial diversity and promote bacteria linked to obesity.

The problem is getting worse across India. NFHS-5 (2019-21) estimates that close to one in four Indian adults is overweight or obese. The World Health Organization also says that approximately 50 percent of Indians do not achieve the recommended levels of physical activity.

When Lifestyle Measures No Longer Work

The foundation of obesity treatment remains healthy eating, exercise, better sleep and ongoing lifestyle changes. They help every person no matter their weight.

Some patients, however, continue to gain weight or remain morbidly obese despite years of diligent effort. In such situations, obesity is a chronic metabolic disease that needs medical treatment.

In South Asian population, the eligibility for bariatric surgery generally begins from a BMI > 29 with comorbidities such as type 2 diabetes, hypertension, dyslipidaemia, obstructive sleep apnoea or joint disease. If BMI is over 35, surgery may be advised depending on the patient's overall clinical state.

Procedures such as sleeve gastrectomy and gastric bypass not only shrink the stomach, but also reset a number of hormonal pathways that originate in the gut. Within days of surgery, before significant weight loss occurs, GLP-1 levels increase, appetite decreases, insulin sensitivity improves, and blood sugar regulation frequently begins to improve.

Long-term data from the ARMMS-T2D study have demonstrated durable weight loss and sustained improvement in diabetes control for many patients more than 10 years after surgery.

Robotic-assisted bariatric surgery further improves surgical precision by providing improved visualisation, refined instrument movement, smaller incision size, reduced blood loss and faster recovery for appropriately selected patients.

Gut-Centered Weight Management

Calories alone cannot explain weight management. Every day the gut modulates hunger, metabolism, inflammation, blood sugar regulation and fat storage via a complex web of hormones, bacteria and metabolic signals.

A healthy gut through a balanced diet, exercise, adequate sleep, and timely medical attention helps maintain a healthier metabolism throughout life. For individuals with severe obesity, evidence-based medical and surgical therapies provide an additional option for improved metabolic health when lifestyle interventions alone do not result in durable outcomes.

One of the results is reflected in the weighting scale. The gut has a role in the way that outcome plays out.

(By Dr. Ashish Gautam, Principal Director, Robotic and Laparoscopic Surgery, Max Super Speciality Hospital, Patparganj, New Delhi)



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