Obesity has become one of the biggest health challenges of modern times. Around the world, rising body weight is linked to higher risks of type 2 diabetes, heart disease, sleep problems, certain cancers, and many other medical conditions.
For years, people trying to lose weight often struggled because lifestyle changes alone do not always produce large or lasting results.
The arrival of medicines such as semaglutide and tirzepatide has changed the conversation around obesity treatment. These drugs have attracted enormous attention because some people have achieved weight loss that once seemed possible only through weight-loss surgery.
Both medicines influence appetite by acting on hormones that help regulate hunger and fullness. Many patients report feeling satisfied after eating smaller amounts of food. This often leads to gradual weight loss over time.
Despite their popularity, doctors have repeatedly seen that patients do not all respond in the same way. Some people lose an impressive amount of weight, while others see only modest changes. Researchers wanted to understand the full range of outcomes that people experience outside clinical trials.
A team led by researcher Venky Soundararajan analyzed anonymous electronic health records from more than 20,000 patients. The scientists created two matched groups, each containing 10,339 patients.
One group received tirzepatide, which is sold under brand names including Mounjaro and Zepbound. The other group received semaglutide, which includes medications such as Ozempic, Wegovy, and Rybelsus.
Their study was published in the journal PNAS Nexus.
The researchers discovered that responses to these medicines varied greatly. Some patients experienced almost no weight loss, while others lost more than 25 percent of their body weight. Such wide differences show that obesity treatment is more complicated than simply prescribing a medication and expecting the same result in everyone.
When average results were compared, tirzepatide appeared to perform better. Patients taking tirzepatide lost an average of 14.7 percent of their body weight over time. In comparison, patients taking semaglutide lost an average of 10.8 percent.
The researchers were especially interested in people who achieved very large weight reductions. They defined these individuals as high responders if they lost more than 15 percent of their body weight within a year. Nearly twice as many patients taking tirzepatide reached this goal compared with those taking semaglutide.
The study also found differences in side effects. Patients receiving tirzepatide reported fewer problems involving stomach symptoms, headaches, and tiredness. These side effects can be important because they often influence whether patients continue taking a medication.
Another notable finding involved differences between patient groups. Women were generally more likely to achieve major weight loss than men. White patients also tended to lose more weight than Black and Hispanic patients, who more often lost less than 5 percent of their body weight.
The researchers stress that these findings do not mean that certain groups cannot benefit from the medications. Instead, the results suggest that important factors affecting treatment response remain poorly understood. Genetics, hormone levels, eating habits, social factors, and other medical conditions may all contribute to the differences.
The study provides useful information because it reflects what happens in routine healthcare settings. Clinical trials often involve carefully selected participants and close monitoring. Real-world studies capture a wider variety of patients and can reveal patterns that may not appear during formal trials.
The findings may eventually help doctors provide more individualized care. Rather than treating obesity as a condition with one solution for everyone, healthcare providers may someday use information about a person’s background, health history, and biology to choose the medication that is most likely to work for that individual.
The study findings suggest that tirzepatide currently offers greater average weight loss and fewer common side effects than semaglutide in everyday medical practice. However, the most important message may be that obesity treatments do not produce identical results in every person.
The research highlights the need to better understand why responses differ and points toward a future in which weight-loss medicine becomes increasingly personalized and tailored to each patient’s needs.
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Source: Harvard Medical School.
