Dr. Andres Acosta, a gastroenterologist and obesity researcher at the Mayo Clinic in Minnesota, has spent years trying to answer a question that puzzles many patients and doctors alike: why does the same weight-loss medication work brilliantly for one person but only modestly for another?

Now, his team may have found part of the answer. A study published in the journal Gastroenterology followed 483 adults with obesity and discovered something striking. About one in four of them had a biological subtype that responded exceptionally well to tirzepatide, a medication that mimics natural hormones involved in controlling appetite and blood sugar. After six months of treatment, these patients lost an average of 21.5% of their body weight. Patients with other subtypes lost 11.7% — nearly half as much.

The key difference appears to be in how their bodies handle fullness. People with this high-responding subtype produce lower levels of hormones like GLP-1, which normally tell your brain you are satisfied after eating. Their stomachs also empty faster, and they report feeling hungrier after meals. The researchers call this the "hungry gut" obesity phenotype.

What surprised the team was where the problem originates. Earlier research had suggested the gut microbiome — the trillions of bacteria living in the intestines — might be partly to blame. But this study found the reduced hormone levels were actually linked to decreased hormone production in the intestine itself, not bacterial differences.

The implications are significant. Obesity increases the risk of diabetes, heart disease, and certain cancers, among other serious health problems. If doctors can identify which patients have this specific subtype before starting treatment, they could potentially match people with the therapy most likely to work for their biology, rather than relying on trial and error.

"Obesity is a complex disease driven by different biological mechanisms," Dr. Acosta said. "Our findings suggest we can begin identifying which patients are most likely to respond to specific therapies rather than treating obesity as a single disease."

The researchers caution that more studies are needed before this approach becomes standard in doctors' offices. But for the millions of people worldwide struggling with obesity, this research represents a meaningful step toward treatment that finally fits each person's unique body.