Only 1.2% developed diabetes versus 12.6% in the placebo group
In a moment when medicine is quietly rewriting what chronic disease must mean, a three-year clinical trial has shown that a weekly injection of tirzepatida reduced the risk of type 2 diabetes progression by 94 percent among adults living with prediabetes and obesity. Published in The New England Journal of Medicine and presented at Obesity Week 2024, the findings suggest that weight itself — long treated as a symptom — may be a lever powerful enough to alter the course of metabolic disease. The drug, sold as Mounjaro and developed by Eli Lilly, now awaits its commercial debut in Brazil, where one in four adults lives with obesity.
- A 94% reduction in diabetes progression is not a marginal improvement — it is a near-erasure of risk, with only 1.2% of treated patients developing diabetes compared to 12.6% in the placebo group.
- Weight loss of up to 22.9% over three and a half years challenges the long-held assumption that meaningful, sustained weight reduction is beyond the reach of most patients.
- The drug's dual mechanism — activating both GIP and GLP-1 receptors to suppress appetite — represents a departure from single-pathway treatments and may explain its outsized results.
- Even after participants stopped taking the drug, the protective gap between treated and untreated groups persisted, raising questions about lasting metabolic reprogramming.
- Brazil approved Mounjaro for diabetes in September 2023, but commercialization has not yet begun, leaving a large at-risk population waiting as regulatory and market timelines slowly converge.
- A head-to-head trial against Wegovy, expected to publish next year, will force a reckoning between two leading drugs — and could reshape prescribing patterns across Latin America and beyond.
Eli Lilly this week released results from a 176-week clinical trial examining whether tirzepatida — sold as Mounjaro — could prevent the progression from prediabetes to type 2 diabetes in adults with obesity or excess weight. The data, published in The New England Journal of Medicine and presented at Obesity Week 2024, delivered a striking answer: a 94 percent reduction in diabetes risk among those who received the drug.
The trial enrolled 1,032 adults, predominantly women with an average age of 48, all of whom had prediabetes and at least one additional condition such as high blood pressure, high cholesterol, or sleep apnea. Participants were divided into groups receiving weekly doses of 5 mg, 10 mg, or 15 mg of tirzepatida, or a placebo — all alongside dietary and lifestyle counseling. The highest dose produced 22.9% body weight loss, compared to just 2.1% in the placebo group. More significantly, only 1.2% of treated patients developed diabetes by the end of the study, versus 12.6% of those on placebo. The protective effect persisted even after the drug was discontinued.
Tirzepatida works by activating two appetite-regulating hormone receptors — GIP and GLP-1 — reducing how much patients want to eat. Side effects were largely gastrointestinal. Eli Lilly's medical director in Brazil described the drug as a revolution in metabolic disease treatment, noting that some patients on the highest dose achieved blood sugar levels below the threshold that defines diabetes.
In Brazil, where roughly one in four adults lives with obesity, Anvisa approved Mounjaro for type 2 diabetes treatment in September 2023, though commercial availability has yet to be announced. Next year, Eli Lilly plans to publish results from a direct comparison with Wegovy, Novo Nordisk's competing drug — a study that could significantly influence how obesity is treated across the region.
Eli Lilly released results this week from a three-year clinical trial that tracked what happens when you give people a weekly injection of tirzepatida—a drug sold under the brand name Mounjaro—and then watch them closely to see if they develop type 2 diabetes. The answer, according to the data published in The New England Journal of Medicine and presented at Obesity Week 2024, was striking: the drug reduced the risk of diabetes progression by 94 percent.
The study enrolled 1,032 adults, most of them women with an average age of 48, who had prediabetes and were either obese or overweight. All of them also had at least one additional health problem—high blood pressure, high cholesterol, sleep apnea, or existing heart disease. Researchers divided them into four groups: three received different doses of tirzepatida (5 milligrams, 10 milligrams, or 15 milligrams) once a week, and one received a placebo. Everyone was also counseled to eat fewer calories and move more. The trial ran for 176 weeks—nearly three and a half years—making it the longest completed study of this drug to date.
The weight loss numbers were substantial. Those who received the lowest dose lost 15.4 percent of their body weight. The middle dose produced a 19.9 percent reduction. The highest dose—15 milligrams—resulted in a 22.9 percent weight loss. By comparison, people in the placebo group lost only 2.1 percent. But the real story lay in what happened to their diabetes risk. Among those treated with tirzepatida, only 1.2 percent were diagnosed with type 2 diabetes by the end of the treatment period. In the placebo group, that number jumped to 12.6 percent. Even after the study ended and participants stopped taking the drug or placebo, the difference persisted: 2.4 percent of the tirzepatida group developed diabetes during the 17-week follow-up, compared to 13.7 percent of those who had received placebo.
Jeff Emmick, a senior vice president at Lilly overseeing product development, framed the findings in clinical terms: a weight loss of up to 22.9 percent corresponded to a hazard ratio of 0.06 for diabetes progression—which translates to that 94 percent risk reduction. Luiz Magno, the medical director of Eli Lilly in Brazil, went further, calling tirzepatida a revolution in metabolic disease treatment. He noted that in diabetes studies, some patients on the highest dose achieved blood sugar control levels—measured by hemoglobin A1c—that fell below 5.7, the threshold that defines non-diabetic status.
Tirzepatida works by activating two different hormone receptors in the body: GIP and GLP-1. Both of these receptors sit in brain regions that control appetite, and the drug appears to work primarily by suppressing how much people want to eat. The most common side effects were gastrointestinal—nausea, diarrhea, and constipation.
In Brazil, the regulatory path is still unfolding. The Brazilian health authority, Anvisa, approved Mounjaro for type 2 diabetes treatment in September 2023, but the company has not yet announced when it will begin selling the drug in the country. Meanwhile, Eli Lilly is preparing to publish results next year from a head-to-head comparison between tirzepatida and Wegovy, a competing drug made by Novo Nordisk that contains semaglutida. That study will test which drug works better for obesity—a condition that affects roughly one in four Brazilian adults.
Notable Quotes
A weight loss of up to 22.9 percent corresponded to a 94 percent reduction in diabetes progression risk.— Jeff Emmick, senior vice president of product development, Eli Lilly
Tirzepatida is a revolution in the treatment of patients with diabetes and metabolic diseases.— Luiz Magno, medical director of Eli Lilly Brazil
The Hearth Conversation Another angle on the story
Why does a three-year study matter more than a shorter one?
Because weight loss and metabolic changes can bounce back. This trial shows the effect held steady for 176 weeks—that's real durability, not just initial enthusiasm wearing off.
The 94 percent figure is striking. But what does it actually mean for a person sitting in a doctor's office?
It means if you're overweight with prediabetes and you take this drug, your odds of developing full diabetes drop dramatically. Instead of roughly 1 in 8 people getting diabetes, it's closer to 1 in 80.
The weight loss—22.9 percent—is that typical for this class of drug?
It's substantial. For context, the placebo group lost 2.1 percent just from being counseled on diet and exercise. So the drug is doing real work beyond behavioral change.
What about the side effects?
Mostly stomach trouble—nausea, diarrhea, constipation. Not trivial, but manageable for most people. The study doesn't say how many people quit because of it.
Why is Brazil waiting to sell this if it's already approved?
Regulatory approval and commercial launch are different things. The company needs to negotiate pricing, set up distribution, handle manufacturing. It's bureaucracy, not doubt about the drug.
What's the Wegovy comparison going to tell us?
Whether this drug or that one works better for obesity specifically. Right now they're in different lanes—Mounjaro is approved for diabetes, Wegovy for weight loss. Head-to-head data could reshape how doctors choose.