The European Congress on Obesity 2026 runs May 12–15 in Istanbul and is the next major obesity-medicine readout cycle after the Q1 earnings season. Novo Nordisk leads the abstract count with 52 presentations spanning the full STEP UP data for Wegovy 7.2 mg (following the April 7 launch and Q1 contribution), CagriSema higher-dose Phase 3 plans (after the February 2026 head-to-head loss against tirzepatide and the May 6 Q1 disclosure that the single-chamber co-formulation was discontinued), Wegovy pill efficacy and tolerability, and women's-obesity, perimenopause, and migraine subgroups.
A 21-expert global panel of obesity and cancer specialists is also expected to formally present a research proposal for a 10-year prospective trial testing GLP-1 receptor agonists for prevention of obesity-related cancers — building on SELECT cardiovascular benefit data, real-world dementia-incidence reductions, and the Lancet Psychiatry mental-health cohort. AstraZeneca's eleglipron full Phase 2b data from VISTA and SOLSTICE is on the ADA 2026 schedule the following month.
Stories here cover ECO readouts and the surrounding obesity-pharmacology calendar. See #wegovy, #cagrisema, and #novo-nordisk.
Published May 12 in Nature Medicine and presented at ECO 2026, the first-of-its-kind ATTAIN-MAINTAIN trial (NCT06584916) tested whether adults who had already lost substantial weight on Wegovy or Zepbound could maintain it after switching to once-daily orforglipron. Over 52 weeks, the semaglutide-switch group regained an average of 1 kg and the tirzepatide-switch group an average of 5 kg, with most cardiometabolic gains preserved. Carel le Roux and Louis Aronne led the analysis.
An ECO 2026 analysis covered May 18 by ScienceDaily examined 89,718 patients starting GLP-1 therapy — 75.6% semaglutide, 17.5% tirzepatide, 6.9% liraglutide — and stratified BMI change at year one. In the first year, 27% reduced BMI by less than 5%, 22.4% by 5-10%, 14.1% by 10-15%, and 15.8% by ≥15%, while 20.8% actually gained weight. Greater weight loss correlated with larger reductions in obesity-related risk endpoints; patients who gained weight after starting treatment faced worse health outcomes than untreated comparators in several measures.
The Lancet formalized SURMOUNT-MAINTAIN on May 14, 2026, the same day the trial was presented at ECO 2026 in Istanbul. The Phase 3b 112-week study from Dr. Deborah Horn and colleagues at UTHealth Houston re-randomized patients who had reached maximum tolerated dose tirzepatide to continue MTD (15 mg or 10 mg), step down to 5 mg, or switch to placebo. Patients continuing MTD were 7x more likely to maintain their weight loss than those switching to placebo; the 5 mg step-down arm was 4x more likely than placebo. At week 112, MTD continuers preserved all of their initial weight loss; 5 mg-step-down patients lost only 5.6 kg of their initial gains on average. The 'seven times more likely' framing — picked up by EurekAlert and the daily science press — is the cleanest patient-facing summary of maintenance economics published to date.
The 33rd European Congress on Obesity closes in Istanbul on Friday May 15 after four days that reframed the obesity-pharmacology conversation around two themes. First, maintenance: the SURMOUNT-MAINTAIN Lancet publication, ATTAIN-MAINTAIN Nature Medicine publication, and Wegovy STEP UP early-responder analyses gave prescribers Phase 3 evidence for dose tapering and switching strategies — moving past the 'how much weight will I lose' question to 'how do I stay there'. Second, guideline alignment: the EASO 2026 Nature Medicine framework formally privileged semaglutide and tirzepatide as first-line therapy across most obesity complications, with complication-specific differentiation (tirzepatide for OSA/MASH; semaglutide for OA/CVD/MASH-fibrosis). Caliway CBL-514 + GLP-1R combination preclinical data and Ascletis next-generation amylin and dual-incretin candidates rounded out the four-day program.
The European Association for the Study of Obesity published an updated pharmacological framework in Nature Medicine, presented at ECO 2026 in Istanbul on Thursday May 14. Semaglutide and tirzepatide are recommended as first-line treatment for obesity across most complications. Tirzepatide is preferred for obstructive sleep apnea and MASH; semaglutide is preferred for knee osteoarthritis and established cardiovascular disease — and is the only agent with current evidence supporting MASH-fibrosis improvement. The framework integrated evidence through November 21, 2025 from 62 randomized controlled trials. The algorithm uses obesity-related complication presence as the primary treatment-selection factor and provides the first major obesity-society guideline to formally privilege incretin-based therapy across the indication mix.
Novo Nordisk's CagriSema REDEFINE 1 cardiovascular sub-analyses, presented at ECO 2026 on Thursday May 14, layered onto the May 12 body-composition data. At week 68, CagriSema (cagrilintide 2.4 mg + semaglutide 2.4 mg) reduced systolic blood pressure by 10.9 mmHg vs 8.8 with semaglutide alone and 2.1 with placebo. High-sensitivity C-reactive protein dropped 68.9% vs 55.4% (semaglutide) and 16.0% (placebo). The 10-year predicted atherosclerotic cardiovascular disease risk decreased meaningfully on CagriSema versus all comparators, with fewer participants on CagriSema falling into the intermediate-to-high-risk category. The sub-analyses sharpen the combination-therapy case beyond the 22.7% mean weight-loss headline.
Prof. Jens-Christian Holm and colleagues at the Children's Obesity Clinic (European Centre for Obesity Management at Holbæk Hospital) presented RESETTLE at ECO 2026 on May 13. The randomized trial enrolled young adults aged 18-28 who remained severely obese despite at least one year of hospital-based non-pharmacological treatment in childhood. After 68 weeks of once-weekly semaglutide 2.4 mg vs placebo, the treatment arm achieved 19% mean BMI reduction (22.3 kg average weight loss). Total fat mass, abdominal fat, and liver fat all improved substantially vs placebo. The data fills a clinical gap — most semaglutide weight-loss trials excluded young adults coming out of structured pediatric obesity programs, leaving prescribers without evidence for one of the most underserved cohorts.
A second body-composition substudy from REDEFINE 1 presented May 14 at ECO 2026 broke out the DXA subgroup by treatment arm. At week 68, CagriSema (cagrilintide 2.4 mg + semaglutide 2.4 mg) produced -23.9% weight reduction in the DXA subgroup, compared with -16.6% on semaglutide 2.4 mg alone, -15.0% on cagrilintide 2.4 mg alone, and -2.8% on placebo. The fat-mass-to-lean-tissue ratios were favorable across all active arms: 66.9% fat-mass contribution on CagriSema, 69.7% on semaglutide, 62.9% on cagrilintide. The cagrilintide monotherapy arm is the first head-to-head body-composition signal for amylin-only therapy at clinically meaningful weight-loss levels — relevant to Zealand and Roche's petrelintide Phase 3 program and the broader amylin-versus-incretin debate.
Eli Lilly published SURMOUNT-MAINTAIN in The Lancet and ATTAIN-MAINTAIN in Nature Medicine on May 12, with concurrent presentation at ECO 2026 in Istanbul. SURMOUNT-MAINTAIN tested lower-dose Zepbound (tirzepatide 5 mg) vs maximum tolerated dose: at week 112, MTD preserved all weight loss while the 5 mg arm lost only 5.6 kg additional. ATTAIN-MAINTAIN tested Foundayo (orforglipron) as a switch from injectable GLP-1s in SURMOUNT-5 participants: orforglipron preserved 79.3% of injectable-phase weight loss vs 37.6% on placebo at week 52; Wegovy MTD switchers regained only 0.9 kg, Zepbound MTD switchers regained 5.0 kg. The dual readout reframes the maintenance-versus-discontinuation conversation: dose-tapering and oral-switching strategies now have Phase 3 evidence behind them, validating the long-term-treatment chronic-disease framing.
Viking Therapeutics presented full 13-week Phase 2 VENTURE-Oral data at ECO 2026 May 12 in Istanbul: once-daily oral VK2735 produced statistically significant, dose-dependent mean weight loss up to 12.2% (26.6 lbs) over 13 weeks with placebo-adjusted significance starting at Week 1. The favorable tolerability profile and rapid early onset of effect support Viking's Q4 2026 plan to initiate a Phase 3 trial of the oral formulation following positive FDA feedback. The data complements the Phase 3 VANQUISH-1 subcutaneous program (4,650 patients enrolled November 2025) and VANQUISH-2 in T2D+obesity (~1,000 patients, enrollment completed March 26, 2026). VK2735's dual GLP-1/GIP mechanism puts it in direct comparison with tirzepatide and the next-generation Mounjaro/Zepbound franchise.
Novo Nordisk presented new OASIS 4 subanalyses of the Wegovy pill (oral semaglutide 25 mg) at ECO 2026 on May 13. Nearly one third (29%) of patients were classified as 'early responders' — losing at least 10% body weight by week 16 — and continued treatment to 64 weeks for a mean 21.6% body weight loss vs 13.2% at four months. A separate physical function analysis showed 77.3% of patients with poor baseline physical function achieved clinically meaningful improvement (bending over, standing comfortably, staying active) vs 42.9% on placebo. The data adds to the OASIS 4 February 2026 16.6% mean weight-loss headline by stratifying patients on early response — a likely tool for prescribers thinking about dose escalation and persistence.
An ORION indirect treatment comparison presented at ECO 2026 on May 13 framed the head-to-head competition between Novo's Wegovy pill (oral semaglutide 25 mg) and Lilly's Foundayo (orforglipron 36 mg). The Wegovy pill delivered statistically significant greater mean weight loss than orforglipron, with patients on orforglipron showing approximately 14x higher odds of discontinuing treatment due to gastrointestinal side effects. The May 13 framing complements Novo's Q1 print disclosure that Wegovy holds 65% of all new US GLP-1 prescriptions; CEO Mike Doustdar's CNBC commentary called the moment a 'turnaround situation' for the Danish company. The ORION ITC matters as a prescriber-decision tool given the two compounds are now the only two FDA-approved oral GLP-1s for chronic weight management.
Novo Nordisk's CagriSema REDEFINE 1 treatment-target analysis presented as an oral presentation at ECO 2026 on May 12 reported that the cagrilintide + semaglutide combination drove a higher percentage of participants to clinically meaningful BMI and waist-to-height ratio (WHtR) targets than any monotherapy or placebo arm. 50.7% of CagriSema-treated participants reached BMI <30 at week 68 vs 10.2% on placebo, and participants reaching BMI <27 plus WHtR <0.53 showed normalization of cardiometabolic parameters at higher rates than non-achievers. A companion REDEFINE 1 cardiovascular risk analysis scheduled for May 14 ECO presentation tracks predicted atherosclerotic CVD risk reduction. The data complements the May 12 body-composition substudy (35.7% fat-mass loss vs 14.4% lean tissue loss).
Sector stock reaction across May 12-13: Novo Nordisk ADRs popped roughly 6% premarket May 12 on the early-responder + women's-data combination and the OASIS 4 mobility analyses; Eli Lilly traded flat as the SURMOUNT-MAINTAIN and ATTAIN-MAINTAIN dual publication confirmed expected maintenance positioning rather than producing fresh upside surprises. Analysts noted the broader 'long-term treatment' thesis — that GLP-1 obesity drugs are chronic-disease medications, not short courses — got concrete trial backing this week between SURMOUNT-MAINTAIN, ATTAIN-MAINTAIN, and STEP UP early-responder analyses. The week's narrative shift sets up the May 14-15 ECO Day 3+4 cycle and the May 29-June 2 ASCO 2026 meeting in Chicago — where peptide-drug conjugates (Bicycle BT8009, Avacta AVA6000, Pfizer FAP-Dox) take the next round of clinical-data spotlights.
A post-hoc analysis of the Phase 3 STEP UP trial presented Tuesday May 12 at ECO 2026 identified an 'early responder' subgroup — patients who lost at least 15% body weight within the first 24 weeks. About 27% of patients on the higher-dose Wegovy 7.2 mg dose met that threshold vs 21% on the 2.4 mg dose and 3% on placebo. Early responders went on to lose a mean 27.7% body weight at week 72 (vs the 21% headline mean across all 7.2 mg patients). The analysis also confirmed that 84% of weight loss across both Wegovy doses came from fat mass, with muscle function preserved. The data sharpens the case for early-response-based dose decisions in the post-launch real-world workflow.
A second post-hoc analysis of STEP UP presented Tuesday found Wegovy 7.2 mg delivered consistent weight loss across reproductive life stages: 22.6% premenopausal, 19.7% perimenopausal, 19.8% postmenopausal, with 41.4% of premenopausal women hitting ≥25% loss. Waist-circumference reductions: 17.5%, 15.6%, 15.3% respectively. Separately, a real-world analysis of 34,000+ women showed that those taking Wegovy had a 42-45% lower migraine risk and a 25% lower depression risk starting six months in versus those on menopausal hormone therapy alone. The real-world data lands as observational signals that warrant prospective study — not as proof of causation — but reinforces the cardiovascular and quality-of-life narrative for the women's-health subgroup.
A prespecified body-composition substudy of REDEFINE 1 presented at ECO 2026 reported that 252 participants on CagriSema 2.4 mg/2.4 mg (semaglutide + cagrilintide) achieved a 35.7% relative reduction in fat mass and a 14.4% reduction in lean soft-tissue mass at week 68 — compared with 5.7% and 4.3% on placebo. The headline 22.7% mean weight reduction in REDEFINE 1 (NEJM publication June 2025) thus broke down with a fat-mass-to-lean-tissue ratio of roughly 2.5:1, a more favorable body-composition profile than the typical 1.5-2:1 ratio reported for GLP-1 monotherapy. The data builds the case for combination amylin-GLP-1 therapy as preferentially fat-selective.
Real-world data presented in the ECO 2026 cycle counters the trial-based efficacy headlines: a Prime Therapeutics commercial claims analysis (cited in the May 2026 Managed Healthcare Executive cover story) found just 8.1% of members persisted with anti-obesity GLP-1 medications for three years. A separate 6-month Medicaid persistence analysis showed roughly 61% staying on treatment at six months. The high attrition is driven primarily by GI tolerability, insurance turnover, and out-of-pocket costs after step-edit programs. For newer agents like semaglutide and tirzepatide, post-discontinuation weight regain averages 0.8 kg per month — projecting return to baseline by ~1.5 years. PBM programs (Optum Rx Weight Engage, Rightway, MedImpact GLP-1 Benefit 360) are now embedding multidisciplinary support to lift persistence above the current floor.