“Beyond Dieting: Expert Explains the Science Behind Obesity and Weight Loss”

Obesity is often viewed as a consequence of overeating or poor self-control.

However, medical science increasingly recognises it as a complex, chronic disease driven by biological, hormonal, genetic, and environmental factors that influence how the body regulates weight.

We speak to Dr Ranjeet Kumar Singh, Consultant (Bariatric Surgery), Regency Health, Kanpur, to understand why obesity cannot be explained by diet alone, and why long-term management often requires a broader medical approach.

Hormonal Imbalance

The body regulates hunger and fat storage through hormones such as leptin, ghrelin, and insulin. In obesity, this regulatory system often becomes disrupted.

Leptin, produced by fat cells, signals the brain when the body has enough energy stored. In many people with obesity, however, leptin resistance develops, meaning the brain no longer responds properly to fullness signals, leading to persistent hunger.

At the same time, ghrelin—the hunger hormone—may remain elevated, increasing appetite and food intake. These hormonal changes can make weight loss significantly more difficult, even with dietary restriction.

According to the World Health Organization, over 1 billion people worldwide are living with obesity, with hormonal and metabolic dysfunction playing a key role alongside lifestyle factors. In India as well, rising urbanisation, stress, processed food consumption, and sedentary habits have contributed to increasing obesity rates.

Procedures such as sleeve gastrectomy can significantly reduce ghrelin levels, thereby lowering appetite and supporting weight loss.

Metabolic Dysfunction

Obesity is also closely linked to how the body manages energy. The “set point” theory suggests that the brain regulates body weight within a certain range, and actively resists changes to it. When calorie intake is reduced, the body may respond by slowing metabolism—a process known as adaptive thermogenesis—which can lead to weight regain after dieting.

Research indicates that genetics may account for 40–70% of differences in body mass index (BMI). Obesity is also associated with metabolic syndrome, which increases the risk of heart disease, diabetes, and other chronic conditions.

Studies show that more than 80% of individuals regain lost weight within five years after dieting, largely due to these biological adaptations. In contrast, bariatric procedures such as gastric bypass have demonstrated improvements in metabolic health and more sustained weight reduction.

Genetics and Environment

Genetic predisposition combined with modern lifestyle factors significantly increases the risk of obesity. Certain gene variants, such as those linked to the FTO gene, have been associated with higher obesity risk by influencing appetite regulation and brain responses to food. This can contribute to stronger cravings and reduced satiety signals.

At the same time, global obesity rates have tripled since 1975, driven primarily by environmental changes such as high-calorie diets, reduced physical activity, and urban lifestyles rather than genetic shifts alone. Newer treatments, including GLP-1 receptor agonist medications, mimic natural gut hormones that regulate appetite and have been shown to support meaningful weight loss in many patients.

Treatment Beyond Diet

While diet and exercise remain important, evidence suggests that they alone often have limited long-term success in sustained weight management because they do not fully address underlying biological mechanisms.

Bariatric surgery targets multiple pathways involved in obesity, including hormonal regulation and metabolic changes. Clinical data from major health institutions indicate significant long-term weight loss outcomes in appropriately selected patients.

However, experts emphasise that obesity management should be individualised. A combination of medical treatment, lifestyle modification, and behavioural support offers the most effective long-term approach.

Early identification using BMI (above 30 kg/m²) and waist circumference can help assess risk and guide intervention. A holistic, medically guided strategy remains key to addressing this growing health challenge.