GLP-1 Therapies Newsletter
Issue #34April 27, 20267 studies

Tirzepatide users had 18.4% weight loss vs 11.9% with semaglutide in head-to-head trial

The weight loss drug wars just got some new data. A head-to-head trial in Japan and Taiwan compared two of the biggest names in obesity treatment—and the results weren't close.

🎯 Tirzepatide beats semaglutide in first major head-to-head obesity trial

  • 331 people with obesity in Japan and Taiwan got either tirzepatide or semaglutide for 68 weeks—both at maximum doses

  • Tirzepatide users lost 18.4% of their body weight on average, compared to 11.9% with semaglutide (a 6.5 percentage point difference)

  • Side effects were similar between groups, with about half experiencing gastrointestinal issues like nausea and vomiting

Why it matters: This is the first large trial to directly compare these two blockbuster weight loss drugs, giving doctors and patients clearer data on which might work better.

🥇 Top 1% journal 🔗 The lancet. Diabetes & endocrinology Journal Article 🗓️ Apr 20

Key Findings

💊 Tirzepatide may reduce heart attack and stroke risk in early-stage metabolic disease

  • 448,591 patients with early cardiovascular-kidney-metabolic syndrome got tirzepatide vs other GLP-1 drugs in real-world data

  • Tirzepatide users had 12% lower risk of progressing to advanced disease stages and 15% lower risk of major heart problems

  • Benefits appeared consistent across age groups, sexes, and whether people had obesity or not

💡 Starting with tirzepatide instead of other GLP-1 drugs may offer better protection against serious cardiovascular complications.
🎖️ Top 10% journal 🔗 Diabetes research and clinical practice Journal Article 🗓️ Apr 20

🔬 Semaglutide works better for weight loss in people without diabetes

  • Analysis of 27 studies found non-diabetic adults lost 14.9% of body weight on semaglutide vs 9.6% in diabetic groups

  • Quality of life improvements and metabolic benefits were also greater in the non-diabetic group

  • High costs and supply shortages remain major barriers to long-term use

💡 People without diabetes may see substantially better weight loss results from semaglutide than those with diabetes.
Top 50% journal 🔗 Health science reports Journal Article 🗓️ Apr 20

🧠 Weight loss drugs may protect against atrial fibrillation—even without losing weight

  • 12,812 patients on GLP-1 drugs had 33% lower risk of developing atrial fibrillation compared to matched controls

  • The heart rhythm protection occurred even in patients who gained weight on the medication

  • Benefits only appeared after 24 months of continuous use, suggesting the effect builds over time

💡 GLP-1 drugs may have direct heart rhythm benefits beyond their weight loss effects.
🥉 Top 5% journal 🔗 Heart rhythm Journal Article 🗓️ Apr 24

⚠️ Rare respiratory depression case linked to semaglutide dose increase

  • 40-year-old person developed excessive sleepiness and morning headaches 4 weeks after increasing semaglutide to 1mg weekly

  • Blood tests showed dangerous CO2 buildup (respiratory acidosis) with normal lung function

  • Symptoms and blood chemistry returned to normal within 3 weeks of stopping the drug

💡 Unexplained sleepiness or breathing changes on GLP-1 drugs may warrant immediate medical evaluation.
🔗 JCEM case reports Case Reports 🗓️ Apr 24

🏥 GLP-1 users had better outcomes after heart valve replacement surgery

  • 1,708 patients with diabetes or obesity undergoing heart valve replacement were matched by GLP-1 use

  • GLP-1 users had 37% lower risk of major cardiovascular events and 39% lower risk of death

  • Benefits included fewer heart attacks, strokes, and heart failure episodes after surgery

💡 GLP-1 drugs may provide significant protection during and after major cardiac procedures.
🔗 The Canadian journal of cardiology Journal Article 🗓️ Apr 22

🦴 Semaglutide linked to fewer fractures in people with diabetes and obesity

  • 19,824 matched pairs of patients with diabetes and obesity were followed for up to 3 years

  • Semaglutide users had 31% lower risk of major bone fractures compared to other diabetes medications

  • No fracture benefit was seen in people with obesity but without diabetes

💡 Semaglutide may offer unexpected bone protection specifically for people managing both diabetes and obesity.
🔗 Diabetes, obesity & metabolism Journal Article 🗓️ Apr 20

Implications

This week's research shows GLP-1 drugs are proving their worth beyond weight loss, with emerging benefits for heart rhythm, bone health, and surgical outcomes. The head-to-head data suggests tirzepatide may be the more potent option, but the broader lesson is that these drugs appear to have wide-ranging protective effects that researchers are still uncovering.

Studies in this issue

Primary sources used for this newsletter.

  1. Effects and safety of combined cagrilintide and semaglutide versus semaglutide alone for overweight or obesity with or without type 2 diabetes in adults from Japan and Taiwan
    main storyThe lancet. Diabetes & endocrinology2026-04-20PMID 42009015
  2. Unexpected high carbon dioxide levels despite normal lung tests in a patient taking semaglutide
    key findingJCEM case reports2026-04-24PMID 42027588
  3. Semaglutide's links to bone health in people with obesity, with and without type 2 diabetes
    key findingDiabetes, obesity & metabolism2026-04-20PMID 42010367
  4. Tirzepatide compared to GLP-1 drugs in slowing heart, kidney, and metabolism problems in real patients
    key findingDiabetes research and clinical practice2026-04-20PMID 42009260
  5. Heart health outcomes with GLP-1 drugs in people with diabetes or obesity having minimally invasive aortic valve replacement
    key findingThe Canadian journal of cardiology2026-04-22PMID 42019817
  6. Semaglutide’s safety, effectiveness, and practical use for weight loss in adults without diabetes
    key findingHealth science reports2026-04-20PMID 42005640
  7. Glucagon-like peptide-1 and the risk of irregular heartbeat, independent of weight loss
    key findingHeart rhythm2026-04-24PMID 42029362

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