Obesity is biology, not willpower: Expert challenges 'eat less, move more' myth

Cristina Petratti has spent more than twenty-five years treating obesity, and she has watched the same conversation repeat itself in her office again and again. A patient arrives carrying shame—the belief that their body is the result of insufficient willpower, insufficient discipline, insufficient self-control. Petratti, a family physician and obesity specialist, has come to see this narrative as not just wrong but actively harmful. In a new book published this year, she argues that obesity is a biological disease, one shaped by genetics, hormones, and the brain's own regulatory systems. The American Medical Association classified it as a chronic disease thirteen years ago. Yet the cultural conversation has not caught up.

The problem, Petratti explains, is that obesity has been treated as a moral failing rather than a medical condition. For decades, the dominant advice has been simple: eat less, move more. The Spanish phrase "menos plato y más zapato"—fewer calories and more steps—became shorthand for the solution. But this is not medicine, Petratti says flatly. It is a slogan, and it has done real damage. It places blame on the patient for a disease they did not choose to have. The condition itself is far more complex. Genetics accounts for between twenty and seventy percent of obesity risk. Layer on top of that hormonal dysregulation, low-grade inflammation, environmental factors, and psychological stress, and what emerges is not a simple equation of calories in versus calories out but a cascade of biological disruptions.

At the heart of this cascade are hormones like leptin, insulin, and ghrelin—chemicals that signal hunger and fullness to the brain. When these hormones become dysregulated, the hypothalamus, which controls appetite and satiety, receives scrambled signals. The person feels hungry even when they have eaten. They feel unable to stop eating. This is not a failure of will. It is biology operating outside conscious control. As fat tissue accumulates and expands beyond what the body's fat cells can safely manage, the tissue itself becomes inflamed and begins releasing toxic factors into the bloodstream. These toxins damage other organs and systems. Obesity is linked to roughly two hundred chronic diseases, from hypertension to sleep apnea.

But biology alone does not explain the full picture. Petratti emphasizes that emotions play a central role. Many of her patients do not eat in response to physical hunger. They eat to calm themselves, to escape difficult feelings, to regulate emotions they cannot otherwise name or process. Food becomes a tool for emotional regulation, and the pattern reinforces itself. Petratti uses emotional diaries with patients to help them distinguish between true physiological hunger—the real need for food that emerges hours after eating, accompanied by physical sensations like stomach pain—and emotional hunger, which arrives suddenly and pulls toward highly palatable foods rich in sugar, salt, and fat. Emotional hunger activates the brain's reward system, flooding it with dopamine. It is not about nourishment. It is about relief.

Many patients with obesity, Petratti notes, do not have a simple food problem. They have disordered eating patterns rooted in emotional dysregulation. They eat compulsively, not restrictively, because restriction itself generates guilt and shame. The cycle perpetuates. Understanding this distinction is crucial because it changes how treatment should work. If obesity is multifactorial—shaped by genetics, hormones, inflammation, and emotional patterns—then treatment must address multiple factors simultaneously.

Exercise, in Petratti's framework, is not primarily about burning calories. It is metabolic medicine. Regular physical activity improves insulin sensitivity, reduces inflammation, regulates appetite, and modulates mood. The prescription she recommends is specific: at least one hundred fifty minutes of cardiovascular exercise per week, combined with three days of strength training. For patients starting out, she suggests simple movements—squats, bicep curls, lunges—performed for ten to fifteen minutes at a time, gradually increasing in frequency and intensity. The goal is not to punish the body through exercise but to activate the body's own regulatory systems.

What Petratti is arguing for is a fundamental shift in how obesity is discussed and treated. The shame and self-blame that patients carry are not incidental to the disease. They are obstacles to healing. When a person is told their obesity is simply a matter of eating less and moving more, they internalize the message that their body is a failure of character. When they inevitably struggle—because the biology is working against them—they blame themselves further. The cycle of guilt and failed attempts deepens. Breaking this cycle requires naming obesity for what it is: a chronic, progressive, multifactorial disease in which the body's own systems have become dysregulated in ways that conscious effort alone cannot overcome. Treatment requires medical intervention, behavioral support, emotional work, and exercise prescribed as therapy, not punishment. Only then can patients begin to heal without the added burden of shame.