GLP-1 Research Cycle Summary — May 28, 2026

This research cycle tracked the most significant developments in the GLP-1 and obesity space as of May 28, 2026, focusing on population-level trends, clinical trial breakthroughs, and AI-driven safety monitoring.

1. Real-World Prescriptions Quadruple; Lilly Overtakes Novo (Epic Research)

A massive study of over 304 million patient records in the Cosmos database by Epic Research revealed that GLP-1 prescriptions among U.S. adults have more than quadrupled since 2021, rising from 1,884 to 8,819 per 100,000 patients. Crucially, Eli Lilly's tirzepatide has officially overtaken Novo Nordisk's semaglutide as the most prescribed GLP-1 in the U.S. (roughly 4,700 vs. 3,900 prescriptions per 100,000 patients in Q1 2026). Over this same period, the national adult obesity rate showed its first signs of decline, dropping from 42.3% to 40.7%.

2. GLP-1s as a Post-Surgical Complement: The BARI-STEP Trial (Nature Medicine)

In a major clinical milestone, the first randomized controlled trial of semaglutide (2.4 mg Wegovy) in patients with poor weight loss or subsequent regain after bariatric surgery was published in Nature Medicine. The BARI-STEP trial demonstrated that 85% of patients on semaglutide lost at least 10% of their body weight (compared to 7% on placebo) over 68 weeks. This establishes a new clinical paradigm where GLP-1s act as a crucial complement—rather than just a competitor—to bariatric surgery, expanding the TAM to the 20% of surgery patients who experience post-surgical failure.

3. AI Scans Reddit to Uncover Hidden Side Effects (Nature Health)

A study published in Nature Health by researchers at the University of Pennsylvania used large language models (LLMs) to scan more than 400,000 Reddit posts from 67,008 self-reported semaglutide and tirzepatide users. The analysis uncovered significant, underreported side effects, including menstrual irregularities (reported by nearly 4% of symptomatic users), body temperature fluctuations (chills, hot flashes), and severe fatigue (which emerged as the second most common complaint). While biologically plausible due to hypothalamic interaction, neither the FDA nor the EMA has issued formal label updates or post-marketing mandates yet, as the findings serve as early safety signals rather than proof of causality.

Investor Takeaways

• Lilly’s Market Leadership: Real-world prescribing data confirms that Eli Lilly’s tirzepatide is winning the market share battle against Novo Nordisk’s semaglutide in the U.S., despite Novo's multi-year head start.
• TAM Expansion and Device Risks: The BARI-STEP results expand the GLP-1 market into post-bariatric surgery care, while further threatening medical device companies that rely on high-risk surgical revisions.
• Digital Safety Monitoring: Social media mining via AI is proving to be a highly effective, rapid-response tool for drug safety, providing earlier signals than traditional clinical registries.