Obesity as a Case Study

Obesity is a striking example. Once, hepatitis B and C were the dominant drivers of liver cancer in the United States and globally; today, obesity and metabolic dysfunction– associated steatotic liver disease (MASLD) have surpassed them. Current estimates suggest that 30–40% of U.S. adults have MASLD, and obesity now accounts for more than one- third of new liver cancer cases in the country. Beyond liver cancer, obesity contributes to at least 13 different cancers recognized by the National Cancer Institute – including colorectal, pancreatic, breast, and endometrial cancers – and is projected to overtake smoking as the leading preventable cause of cancer in the coming decades. And we don’t need to be reminded of all those numerous conditions obesity leads to: heart disease, stroke, vascular disease, diabetes, and other metabolic conditions.

The medical response has been powerful: bariatric surgery, which now exceeds 250,000 procedures annually in the U.S., and new pharmacologic therapies such as semaglutide and tirzepatide (Ozempic, Wegovy, Mounjaro). Never mind the soaring healthcare costs associated with these treatments. They are transformative for some patients – lifesaving, even. But for the vast majority, the crisis could be mitigated earlier through effective prevention: healthier diets, physical activity, and structural changes to food and built environments. Yet medical education devotes little time to nutrition or prevention, leaving physicians far better prepared to prescribe medication after obesity takes hold than to prevent it in the first place.

A Reactive System in a Preventable Era

Meanwhile, the landscape of disease has shifted. Infections are no longer the dominant killers in the U.S.; instead, chronic diseases – obesity, diabetes, cardiovascular disease, and cancer – now lead. These conditions are shaped by lifestyle, social determinants, and structural inequities. Yet we continue to equip physicians with the tools of a 20th- century biomedical system to solve the problems of a 21st- century chronic disease epidemic.

Much of today’s medicine still waits for disease to appear before acting. We step in after arteries clog, stomachs ulcerate, or tumors grow-deploying extraordinary diagnostics and treatments when it is already late. Patients deserve more. They need physicians who can explain not only what is wrong but how it might have been prevented. Even better, they deserve physicians who intervene earlier, offering clear guidance to keep arteries open, stomachs intact, and tumors from forming at all.

Toward a Prevention-First Future

If prevention were woven into the very fabric of medical education, physicians would graduate with as much fluency in addressing lifestyle, behavioral, and structural risks as they have in interpreting scans or prescribing medications. This would not compete with innovation – it would complement it. Artificial intelligence, genomics, and precision therapeutics could then be used not only to treat disease, but to predict, prevent, and reduce risk before disease takes hold.

The future of medicine cannot rest solely on diagnostics and therapies. It must be anchored in prevention, taught from the first year of premedical education through residency and beyond. Otherwise, we risk continuing to train doctors for yesterday’s challenges while today’s patients – still asking “Can you tell me what is wrong with me?” – leave without the answers, guidance, and preventive strategies they truly need.