Contrary to what you might have been told, Ozempic is not a weight-loss drug—at least, not officially. The Novo Nordisk injection has been approved by the U.S. Food and Drug Administration (FDA) for the treatment of type 2 diabetes, but that hasn't stopped doctors from prescribing it off-label for weight loss. The same is true of competitor Mounjaro, made by Eli Lilly. But while both these medications have helped people shed stubborn pounds, a new study found that Ozempic may not be the better option of the two.
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The study, which was published in JAMA Internal Medicine on July 8, looked at patients taking tirzepatide (the active ingredient in Mounjaro) or semaglutide (the active ingredient in Ozempic) in doses approved for the treatment of type 2 diabetes.
Roughly half of the study participants had a recorded type 2 diabetes diagnosis, while the other half didn't have a diabetes diagnosis on record. According to CNN, this likely means that those without diabetes were using the medications for off-label weight management per a doctor's recommendation. (Eli Lilly's tirzepatide drug Zepbound and Novo Nordisk's semaglutide drug Wegovy are FDA-approved for weight loss, containing higher dosages of the active ingredient.)
Researchers evaluated "on-treatment weight loss" and the occurrence of gastrointestinal (GI) side effects in participants, who were either overweight or had obesity. According to findings, patients taking tirzepatide "were significantly more likely to achieve weight loss," and changes in weight were larger for patients on tirzepatide after three months, six months, and 12 months of treatment.
Still, both tirzepatide and semaglutide proved effective for weight loss. Most people on the medications lost 5 percent or more of their body weight after a year. However, more people taking tirzepatide with and without type 2 diabetes reached this benchmark.
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"GLP-1 medications have dramatically increased in use by patients with and without type 2 diabetes in the past year, yet little real-world data exist to compare the effectiveness of two of the most common medications, semaglutide and tirzepatide," lead study author Tricia Rodriguez, PhD, MPH, principal applied scientist at Truveta Research, said in a press release. "That’s what makes today’s study findings so exciting and important."
She continued, "Because Truveta Data provides timely, complete EHR data—including prescriptions and medication dispense data—that captures a large and diverse patient population, we’ve been able to compare the head-to-head efficacy of these two important medications for weight loss in advance of smaller randomized clinical trials. This study can help to inform patient care and outcomes today, not months from now.”
When looking at rates of GI adverse events, reports were similar for patients on both treatments. Researchers specifically looked at moderate to severe side effects such as bowel obstruction, cholecystitis (inflammation of the gallbladder), gallstones, intestinal infection, pancreatitis, and gastroparesis (stomach paralysis). Researchers did not evaluate the incidence of nausea and vomiting, which are classified as mild adverse events.
Rates of treatment discontinuation were also similar. Within 12 months, 55.9 percent of patients on tirzepatide stopped taking it, compared with 52.5 percent of those on semaglutide.
Findings were first published in preprint in 2023, and at that time, Novo Nordisk told CNN that the study didn't present a fair comparison.
"The doses of semaglutide evaluated in this analysis have not been investigated for chronic weight management, and there are no head-to-head trials that have reported which evaluate Wegovy and tirzepatide," a spokesperson told the outlet.
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For the study, patients who were on tirzepatide were taking 10 milligrams per week, while those taking semaglutide were taking 2.4 milligrams per week.
In a statement to Best Life, Novo Nordisk pointed out "key limitations" of the study, specifically the inclusion of patients with type 2 diabetes (as weight loss effects are different in patients with and without the condition), the lack of comparison to Wegovy (even though weight loss was the main objective), and "lacking data" about dose titration.
"More people than ever are taking an active role in diagnosing and treating obesity, so new data is great for patients and healthcare professionals who treat them. However, the ideal way to compare two treatments is an adequately powered head-to-head randomized clinical trial (RCT) in obesity. Currently, no head-to-head trials have been completed comparing tirzepatide and semaglutide 2.4 mg," the spokesperson said.
They concluded, "While lowering body weight is an important goal of obesity management, it is important to also consider other needs when choosing a treatment. Only Wegovy is proven to both help adults with obesity lose excess body weight and keep it off and reduce the risk of major adverse cardiovascular events in adults with known heart disease and either obesity or overweight."
