“Weight Loss Isn’t Just About Diet: Expert Breaks Down the Science of Obesity”

Obesity is often misunderstood as simply the result of overeating or a lack of self-control.

However, medical research shows it is a complex, chronic disease shaped by deep biological processes that influence how the body regulates weight, energy, and appetite.

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 medically guided, holistic approaches.

Hormonal Imbalance

The human body relies on hormones such as leptin, ghrelin, and insulin to regulate hunger, fullness, and fat storage. In obesity, this system often becomes disrupted.

Leptin, produced by fat cells, signals the brain when energy stores are sufficient. However, many individuals with obesity develop leptin resistance, meaning the brain fails to register fullness, leading to continued hunger.

At the same time, ghrelin—the hormone that stimulates appetite—may remain elevated, further increasing food cravings and hunger signals. Research suggests that ghrelin levels in such cases can rise significantly, making weight control more difficult.

According to the World Health Organization, over 1 billion people globally are affected by obesity, with hormonal dysregulation playing a key role alongside lifestyle factors. In India, rapid urbanisation, sedentary behaviour, stress, and processed diets have contributed to rising obesity rates in urban populations.

Procedures such as sleeve gastrectomy can reduce ghrelin levels substantially, which in turn helps decrease hunger and supports weight loss.

Metabolic Dysfunction

Obesity is not only about calorie intake but also about how efficiently the body processes and stores energy.

The “set point” theory suggests that the brain, particularly the hypothalamus, regulates and defends a certain body weight, making sustained weight loss difficult. When calorie intake drops, the body may respond by slowing metabolism—a process known as adaptive thermogenesis—leading to weight regain.

Genetic studies, including twin research, indicate that 40–70% of differences in body mass index (BMI) may be influenced by heredity. Obesity is also closely linked with metabolic syndrome, which increases the risk of cardiovascular disease.

Studies show that more than 80% of people regain lost weight within five years of dieting, largely due to these biological adaptations. In contrast, bariatric procedures such as gastric bypass have been shown to improve metabolic function and support more sustained weight reduction.

Genetics and Environment

Genetics can significantly influence how the body responds to food and stores fat, but environmental factors play a major role in triggering obesity.

Variants of the FTO gene, present in a significant portion of the population, have been associated with increased obesity risk by affecting brain responses to food and satiety. This may contribute to heightened cravings often described as “food noise,” driven by reward pathways in the brain.

At the same time, global obesity rates have tripled since 1975, driven largely by lifestyle changes such as high-calorie diets, reduced physical activity, and urban living patterns, rather than genetic change alone.

Emerging treatments, including GLP-1 receptor agonist medications, mimic natural gut hormones that regulate appetite and have been shown to support 15–20% body weight reduction in many cases.

Treatment Beyond Diet

Despite being widely recommended, traditional diet-based approaches alone have limited long-term success, with studies suggesting low sustained weight-loss maintenance rates over time, as they do not address underlying biological drivers.

Bariatric surgery, by contrast, targets multiple mechanisms including hormone regulation and metabolic function. Clinical data, including findings from institutions like the Cleveland Clinic, indicate significant and sustained weight loss outcomes in suitable candidates over long-term follow-up.

However, experts emphasize that surgery is not the only solution. Effective obesity management requires a combination of medical treatment, lifestyle modification, and behavioural support tailored to individual risk factors.

Simple measures such as BMI assessment (above 30 kg/m²) and waist circumference can help identify risk early. Ultimately, a comprehensive, medically guided approach offers the best chance of managing this growing global health challenge.