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Struggling to lose weight? A bariatric expert explains how metabolism, hormones, and brain signals work against dieting, making obesity a biological not willpower issue.
Weight loss isn’t just about willpower, your brain, hormones, and metabolism actively work to resist it, making obesity a complex biological condition.
If losing weight were simply about eating less and moving more, obesity wouldn’t be such a widespread struggle. Yet millions of people follow strict diets, exercise regularly, and still find themselves stuck or worse, gaining the weight back. The truth is uncomfortable but crucial: your body may be actively working against your weight loss efforts.
“Obesity is not a failure of discipline, it is a chronic biological condition where the body actively resists weight loss,” says Dr. (Prof) Sandeep Aggarwal, Chairman – Manipal Institute of Minimal Access, Bariatric, GI & Robotic Surgery, Manipal Hospital, Dwarka, New Delhi.
When a person reduces calorie intake, the brain does not interpret it as a health goal but as a potential threat to survival.
“The body perceives calorie restriction as a form of famine and activates protective mechanisms,” explains Dr Aggarwal. “It slows metabolism and increases the drive to eat.”
This internal battle is what makes sustained weight loss so difficult.
“The brain becomes hyper-focused on high-calorie foods, amplifying hunger signals while suppressing the signals that indicate fullness,” he adds.
How the Body Fights Back
Weight loss is often interpreted by the body as starvation, triggering survival responses designed to protect stored fat. Several biological mechanisms quietly work against dieting:
The Metabolic Brake:
“When calorie intake drops, the body becomes more energy-efficient,” says Dr Aggarwal. “Basic functions like heart rate and temperature regulation slow down to conserve energy.”
The Hunger Hormone Spike:
“Levels of ghrelin, the hormone that stimulates hunger increase significantly, while leptin, which signals fullness, decreases,” he explains. “This leads to persistent hunger, even after eating.”
The Fullness Signal Weakens:
“Leptin is produced by fat cells. As fat stores shrink, leptin levels fall, making the brain think the body is starving, even if sufficient food has been consumed,” notes Dr Aggarwal.
Fat Cells Fight Back:
“The brain maintains a ‘set point’ weight. When weight drops below this level, the hypothalamus triggers mechanisms to restore it,” he says. “This includes slowing metabolism and increasing appetite.”
Cravings Intensify:
“The brain becomes more sensitive to high-calorie foods, making sugar and fat much harder to resist,” he adds.
How Can It Be Treated?
When obesity becomes resistant to diet and exercise alone, treatment must move beyond willpower-based approaches.
“Modern obesity management focuses on correcting the biological signals that drive hunger, fat storage, and weight regain,” says Dr Aggarwal.
This may include medically supervised nutrition plans tailored to an individual’s metabolic needs, as well as metabolic or bariatric surgery for eligible patients.
“These procedures do not just reduce stomach size, they alter gut hormones,” he explains. “This helps reset the brain’s ‘set point’ and reduces constant hunger signals, allowing the body to stabilise at a lower weight.”
Why Weight Regain Is So Common
Even after weight loss, the body remains in a defensive mode.
“Metabolism often does not return to its previous level, meaning individuals need to consume fewer calories than others just to maintain their weight,” says Dr Aggarwal.
This explains why weight regain is so common and frustrating. “The struggle is not a sign of a weak mind,” he concludes. “It is the result of a strong biological system doing exactly what it is designed to do, protect the body and ensure survival.”
March 29, 2026, 14:33 IST
