Science
Mounjaro bests Ozempic for weight loss in first head-to-head comparison of real-world use
In the first head-to-head comparison of two blockbuster drugs used in real-world conditions, people who took Mounjaro lost significantly more weight than their counterparts who took Ozempic — and the longer the patients kept taking the drugs, the wider the gap became.
After three months of weekly injections, patients on Ozempic lost 3.6% of their body weight, on average, while those on Mounjaro lost an average of 5.9%.
At the six-month mark, Ozempic patients had dropped an average of 5.8% of their weight, while the average weight loss for Mounjaro patients was 10.1%.
And when a full year had passed, those taking Ozempic had lost an average of 8.3% of their weight, while those taking Mounjaro had shed an average of 15.3%.
The researchers who conducted the analysis also found that compared with people on Ozempic, those on Mounjaro were 2.5 times more likely to lose at least 10% of their initial weight and more than three times as likely to lose at least 15% of their weight during their first year on the medications.
The findings were published Monday in JAMA Internal Medicine.
Dr. Matthew Freeby, an endocrinologist and director of the Gonda Diabetes Center at UCLA’s Geffen School of Medicine, said the study results are in line with what he has observed in his own patients.
“From a weight-loss perspective, and from a sugar-lowering perspective for those with Type 2 diabetes, we see stronger effects with Mounjaro compared to Ozempic,” said Freeby, who was not involved in the research.
Both drugs were approved by the U.S. Food and Drug Administration to help people with diabetes keep their blood sugar under control. By mimicking a hormone called glucagon-like peptide 1, or GLP-1, they boost the body’s production of insulin, slow digestion, increase feelings of satiety and reduce appetite.
Mounjaro also imitates a related hormone called glucose-dependent insulinotropic peptide, or GIP.
When the drugs were tested against placebos in clinical trials, both helped patients lose a significant amount of weight. Tirzepatide, the active ingredient in Mounjaro, appeared to be more effective than semaglutide, the active ingredient in Ozempic. But the trials weren’t conducted under the same conditions, so the results aren’t directly comparable.
Researchers from Truveta, a healthcare data and analytics company owned by 30 health systems, sought to remedy that by examining their trove of electronic health records. The work also gave them a chance to see how patients fared outside the idealized setting of a clinical trial, which typically provides free medication, regular check-ups and other types of support.
With the help of their database, the researchers were able to spot people who filled their first prescription for either drug between May 2022 — the month Mounjaro joined Ozempic in receiving FDA approval — and September 2023. Patients didn’t need to have Type 2 diabetes to be included in the study, but they did have to be overweight (with a body mass index of at least 27) or obese (with a BMI of at least 30).
The Truveta team found about 41,000 people across more than 30 states who met all their criteria for being included in the study. Since Ozempic patients outnumbered Mounjaro patients by a margin of 3-to-1, the researchers used information on age, race, income, health history and other factors to come up with a group of Ozempic patients that most closely matched the Mounjaro patients. The result was a population of nearly 18,400 who were evenly split between the two drugs.
Before their first medication dose, the average weight for people in both groups was 243 pounds. But it didn’t take long for the two groups to diverge.
After accounting for unmeasured influences that could have skewed the results, the Truveta team found that the amount of weight lost was 2.4 percentage points higher for Mounjaro patients than for Ozempic patients after three months, 4.3 percentage points higher after six months, and 6.9 percentage points higher after a year.
Mounjaro also bested Ozempic in terms of people’s success in meting various milestones within a year of starting on one of the drugs.
Nearly 82% of Mounjaro patients lost at least 5% of their body weight, compared with 67% of patients who took Ozempic. Likewise, 62% of Mounjaro patients and 37% of Ozempic patients lost at least 10% of their initial weight, while 42% of Mounjaro patients and 18% of Ozempic patients lost at least 15% of their starting weight.
The researchers didn’t examine the biological mechanisms of the two drugs, but study leader Tricia Rodriguez, a principal applied scientist with Truveta Research, said Mounjaro may have been more effective because it works two ways instead of just one.
The big gap in effectiveness wasn’t accompanied by a measurable difference in the rate of moderate or severe side effects like bowel obstructions and pancreatitis, which were rare for patients in both groups. The researchers didn’t compare the risk of milder problems like nausea and vomiting because people wouldn’t necessarily report them to their doctors, Rodriguez said.
Regardless of which drug they took, patients with Type 2 diabetes lost less weight than patients without the disease, the researchers found. That might be explained by the fact that certain diabetes treatments can cause weight gain, and that some patients eat more throughout the day to keep their blood sugar from getting too low, Freeby said.
It’s also possible that people who sought prescriptions for Ozempic or Mounjaro with the goal of slimming down were more motivated to keep taking the drug even if it was expensive or caused uncomfortable side effects, or that they were more likely to adopt other behaviors that promote weight loss, Rodriguez said.
Figuring this out is “a crucial topic for future research,” she said.
People currently taking Ozempic likely have a more pressing question on their minds: Should I switch to Mounjaro?
Dr. Nick Stucky, an infectious disease physician at Providence Portland Medical Center and the study’s senior author, said the results alone should not cause patients to stop taking a drug that is working for them. The risk of side effects, insurance coverage and drug availability are things to consider as well.
“While tirzepatide was significantly more effective than semaglutide, patients on both medications experienced substantial weight loss,” said Stucky, who is also Truveta’s vice president of research.
Freeby seconded that opinion.
“If someone is doing well with a medication, why rock the boat?” he said.
Freeby added that Ozempic (and its sister medication Wegovy, which is FDA-approved specifically for weight loss) has at least one advantage over Mounjaro (and Zepbound, its weight-loss counterpart): In clinical trials, Ozempic has been shown to reduce the risk of heart attacks, strokes and other cardiovascular problems as well as kidney failure.
“At this point, we don’t have a lot of data on Mounjaro when it comes to secondary outcomes,” he said.
Science
What’s in a Name? For These Snails, Legal Protection
The sun had barely risen over the Pacific Ocean when a small motorboat carrying a team of Indigenous artisans and Mexican biologists dropped anchor in a rocky cove near Bahías de Huatulco.
Mauro Habacuc Avendaño Luis, one of the craftsmen, was the first to wade to shore. With an agility belying his age, he struck out over the boulders exposed by low tide. Crouching on a slippery ledge pounded by surf, he reached inside a crevice between two rocks. There, lodged among the urchins, was a snail with a knobby gray shell the size of a walnut. The sight might not dazzle tourists who travel here to see humpback whales, but for Mr. Avendaño, 85, these drab little mollusks represent a way of life.
Marine snails in the genus Plicopurpura are sacred to the Mixtec people of Pinotepa de Don Luis, a small town in southwestern Oaxaca. Men like Mr. Avendaño have been sustainably “milking” them for radiant purple dye for at least 1,500 years. The color suffuses Mixtec textiles and spiritual beliefs. Called tixinda, it symbolizes fertility and death, as well as mythic ties between lunar cycles, women and the sea.
The future of these traditions — and the fate of the snails — are uncertain. The mollusks are subject to intense poaching pressure despite federal protections intended to protect them. Fishermen break them (and the other mollusks they eat) open and sell the meat to local restaurants. Tourists who comb the beaches pluck snails off the rocks and toss them aside.
A severe earthquake in 2020 thrust formerly submerged parts of their habitat above sea level, fatally tossing other mollusks in the snail’s food web to the air, and making once inaccessible places more available to poachers.
Decades ago, dense clusters of snails the size of doorknobs were easy to find, according to Mr. Avendaño. “Full of snails,” he said, sweeping a calloused, violet-stained hand across the coves. Now, most of the snails he finds are small, just over an inch, and yield only a few milliliters of dye.
Science
Video: This Parrot Has No Beak, But Is at the Top of the Pecking Order
new video loaded: This Parrot Has No Beak, But Is at the Top of the Pecking Order
By Meg Felling and Carl Zimmer
April 20, 2026
Science
Contributor: Focus on the real causes of the shortage in hormone treatments
For months now, menopausal women across the U.S. have been unable to fill prescriptions for the estradiol patch, a long-established and safe hormone treatment. The news media has whipped up a frenzy over this scarcity, warning of a long-lasting nationwide shortage. The problem is real — but the explanations in the media coverage miss the mark. Real solutions depend on an accurate understanding of the causes.
Reporters, pharmaceutical companies and even some doctors have blamed women for causing the shortage, saying they were inspired by a “menopause moment” that has driven unprecedented demand. Such framing does a dangerous disservice to essential health advocacy.
In this narrative, there has been unprecedented demand, and it is explained in part by the Food and Drug Administration’s recent removal of the “black-box warning” from estradiol patches’ packaging. That inaccurate (and, quite frankly, terrifying) label had been required since a 2002 announcement overstated the link between certain menopause hormone treatments and breast cancer. Right-sizing and rewording the warning was long overdue. But the trouble with this narrative is that even after the black-box warning was removed, there has not been unprecedented demand.
Around 40% of menopausal women were prescribed hormone treatments in some form before the 2002 announcement. Use plummeted in its aftermath, dipping to less than 5% in 2020 and just 1.8% in 2024. According to the most recent data, the number has now settled back at the 5% mark. Unprecedented? Hardly. Modest at best.
Nor is estradiol a new or complex drug; the patch formulation has existed for decades, and generic versions are widely manufactured. There is no exotic ingredient, no rare supply chain dependency, no fluke that explains why women are suddenly being told their pharmacy is out of stock month after month.
The story is far more an indictment of the broken insurance industry: market concentration, perverse incentives and the consequences of allowing insurance companies to own the pharmacy benefit managers that effectively control drug access for the majority of users. Three companies — CVS Caremark, Express Scripts and OptumRx — manage 79% of all prescription drug claims in the United States. Those companies are wholly owned subsidiaries of three insurance behemoths: CVS Health, Cigna and UnitedHealth Group, respectively. This means that the same corporation that sells you your insurance plan also decides which drugs get covered, at what price, and whether your pharmacy can stock them. This is called vertical integration. In another era, we might have called it a cartel. The resulting problems are not unique to hormone treatments; they have affected widely used medications including blood thinners, inhalers and antibiotics. When a low-cost generic such as estradiol — a medication with no blockbuster profit margins and no patent protection — runs into friction in this system, the friction is not random. It is structural. Every decision in that chain is filtered through the same corporate profit motive. And when the drug in question is an off-patent estradiol patch that has negligible profit margins because of generic competition but requires logistical investment to keep consistently in stock? The math on “how much does this company care about ensuring access” is not complicated.
Unfortunately, there is little financial incentive to ensure smooth, consistent access. There is, however, significant financial incentive to steer patients toward branded alternatives, or simply to let supply tighten — because the companies aren’t losing much profit if sales of that product dwindle. This is not a conspiracy theory: The Federal Trade Commission noted this dynamic in a report that documented how pharmacy benefit managers’ practices inflate costs, reduce competition and harm patient access, particularly for independent pharmacies and for generic drugs.
Any claim that the estradiol patch shortage is meaningfully caused by more women now demanding hormone treatments is a distraction. It is also misogyny, pure and simple, to imply that the solution to the shortage is for women’s health advocates to dial it down and for women to temper their expectations. The scarcity of estradiol patches is the outcome of a broken system refusing to provide adequate supply.
Meanwhile, there are a few strategies to cope.
- Ask your prescriber about alternatives. Estradiol is available in multiple formulations, including gel, spray, cream, oral tablet, vaginal ring and weekly transdermal patch, which is a different product from the twice-weekly patch and may be more consistently available depending on manufacturer and region.
- Consider an online pharmacy. Many are doing a good job locating and filling these prescriptions from outside the pharmacy benefit manager system.
- Call ahead. Patch shortages are inconsistent across regions and distributors. A call to pharmacies in your area, or a broader geographic radius if you’re able, can locate stock that your regular pharmacy doesn’t have.
- Consider a compounding pharmacy. These sources can sometimes meet needs when commercially manufactured products are inaccessible. The hormones used are the same FDA-regulated bulk ingredients.
Beyond those Band-Aid solutions, more Americans need to fight for systemic change. The FTC report exists because Congress asked for it and committed to legislation that will address at least some of the problems. The FDA took action to change the labeling on estrogen in the face of citizen and medical experts’ pressure; it should do more now to demand transparency from patch manufacturers.
Most importantly, it is on all of us to call out the cracks in the current system. Instead of repeating “there’s a patch shortage” or a “surge in demand,” say that a shockingly small minority of menopausal women still even get hormonal treatments prescribed at all, and three drug companies control the vast majority of claims in this country. Those are the real problems that need real solutions.
Jennifer Weiss-Wolf, the executive director of the Birnbaum Women’s Leadership Center at New York University School of Law, is the author of the forthcoming book “When in Menopause: A User’s Manual & Citizen’s Guide.” Suzanne Gilberg, an obstetrician and gynecologist in Los Angeles, is the author of “Menopause Bootcamp.”
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