The study signifies that tirzepatide, the active ingredient in Eli Lilly's Mounjaro and Zepbound, results in greater weight loss compared to semaglutide, found in Novo Nordisk's Ozempic and Wegovy. Circulated in JAMA Internal Medicine, this research is the first direct comparison of these popular weight loss drugs.
Comparative Effectiveness of Zepbound and Wegovy in Weight Loss
Zepbound, approved for weight loss in late 2023, seemed more effective than Wegovy, with patients losing about 21% of their body weight over 72 weeks, compared to 15% over 68 weeks with Wegovy.
However, a direct comparison was challenging without a head-to-head study, as both drugs belong to a class of medications called GLP-1s.
Lead author Tricia Rodriguez, a principal applied scientist at Truveta Research, noted that despite the increased use of GLP-1s, there was limited information on direct comparisons.
The research determined health records of over 41,000 overweight or obese adults who have required either drug, including patients with Type 2 diabetes. More than 9,100 were on tirzepatide, and over 32,000 on semaglutide.
Weight loss was measured at 3, 6, and 12 months. On average, semaglutide users lost 3.6% of their body weight after 3 months, 5.8% after 6 months, and 8.3% after 12 months.
Tirzepatide users encountered better weight loss: 5.9% after 3 months, 10.1% after 6 months, and 15.3% after 12 months.
Rodriguez noted that while both treatments resulted in important weight loss, tirzepatide led to noticeably higher declines. No important difference in serious side effects, such as gastroparesis, was found between the two drugs.
GLP-1 drugs like semaglutide and tirzepatide imitate a hormone that lessens appetite, but tirzepatide also mimics GIP, a hormone that enhances sugar and fat metabolism.
Further randomized, controlled trials are needed for definitive comparisons. Eli Lilly is administering a phase 3 trial with 700 patients, anticipated to end in November, according to ClinicalTrials.gov.
Novo Nordisk emphasized the study's restrictions, such as including patients with Type 2 diabetes, who generally find weight loss more difficult, and inadequate data on primary and progressive doses.
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Experts' Perspective on Tirzepatide and Semaglutide
Dr. Susan Spratt from Duke Health acknowledged tirzepatide's effectiveness but emphasized that both drugs offer significant weight loss compared to current options. She also called for more studies on other health outcomes beyond weight loss.
Semaglutide has been shown to reduce cardiovascular risks and complications from kidney disease in Type 2 diabetes patients, while tirzepatide may help with obstructive sleep apnea.
Dr. Daniel Maselli from True You Weight Loss supported the study's findings but stressed that weight loss is just one factor in prescribing weight loss drugs, considering individual patient needs and medication tolerance.
Novo Nordisk emphasized that the study focused on Mounjaro and Ozempic, not including Wegovy, and raised concerns about insufficient data on participant dosages. They advocated for adequately powered randomized clinical trials (RCTs) for a more robust comparison. Meanwhile, Lilly indicated ongoing RCTs studying tirzepatide and semaglutide in obesity, with results expected later this year.
Novo Nordisk also noted that a significant number of participants used Ozempic off-label, lacking Type 2 diabetes, potentially influencing study outcomes.
The researchers highlighted greater weight loss among participants without Type 2 diabetes, suggesting further research to understand these nuances and patient motivations.
Additional insights are needed into the complex dynamics influencing outcomes for both diabetic and non-diabetic patients, according to the study authors.
Related Article: Tirzepatide Found in Zepbound and Mounjaro Reduces the Severity of Sleep Apnea, Study Reveals
