The 33rd European Congress on Obesity (ECO 2026), held in Istanbul, Türkiye from 12^th to 15^th May, marked a subtle but clear turning point for the obesity conversation. Obesity is no longer framed primarily as a problem of achieving weight loss; it is increasingly understood as a challenge of sustaining weight loss over time.

Across both academic and industry plenary sessions, a consistent set of themes emerged. Maintenance, muscle preservation, population-specific care, and more sophisticated definitions of disease moved to centre stage. The focus is shifting away from solely focusing on topline metrics such as body mass index (BMI) towards metrics more reflective of obesity related risk, such as height to waist ratio, or body composition, and from percentage BMI reduction to “treat to target” focus on a target height to waist or BMI goal. With the announcement of the results of ATTAIN-MAINTAIN, there was the clear emergence of weight maintenance as a focus alongside weight loss, and with it a growing sense of movementowards longer-term outcomes. Together, these themes point to a more mature model of obesity care, one that treats obesity as a chronic condition requiring durable, lifelong management.

Maintenance: ATTAIN-MAINTAIN and SURMOUNT-MAINTAIN

One of the pivotal insights from ECO2026 was Eli Lilly’s industry symposium showcasing ATTAIN-MAINTAIN and SURMOUNT-MAINTAIN results. Breakthrough phase 3 results showed that at week 52, participants who switched from the maximal tolerated dose of semaglutide to orflorglipron (the newly approved Foundayo) maintained all but 0.9 kg of their previously achieved weight loss, while those who switched from the maximal tolerated dose of tirzepatide MTD to orflorglipron maintained all but 5.0 kg. Meanwhile, in SURMOUNT-MAINTAIN patients who had achieved weight loss on tirzeptide over 60 weeks entered a 52 week maintenance phase. They were randomised to continue tirzeptide, reduce the dose to 5 mg, or switch to placebo. Data published in the Lancet showed near-complete weight-loss maintenance on maximum tolerated tirzepatide through Week 112, while a 5 mg step-down dose was associated with 5.6 kg regain on average ¹.

Together, these studies framed maintenance as one of the central conversations at ECO 2026, moving it from an acknowledged challenge to an actionable goal. The ATTAIN MAINTAIN and SURMOUNT MAINTAIN results provide cornerstone evidence that weight loss strategies can be sustained over the long term, rather than treated as time limited interventions. The implications are significant. Maintenance reframes obesity care around durability, shifting attention from how much weight can be lost to how weight loss can be preserved over time. It reinforces obesity as a chronic condition that requires ongoing planning beyond the initial phase of treatment, with greater emphasis on long term outcomes, treatment continuity, and patient experience.

STEP UP: Semaglutide 7.2mg

Whilst maintenance framed the conversation, efficacy still commanded attention. Among the most discussed data at ECO 2026 were results from STEP UP, evaluating semaglutide 7.2 mg. Early responders, defined as participants achieving at least 15% weight loss by week 24, went on to achieve an average weight loss of 27.7% by week 72, compared with 24.8% among early responders receiving 2.4 mg². These findings extend the upper boundary of what has been demonstrated with single agent pharmacotherapy and underline how far weight loss with obesity pharmacotherapy can go.

The concept of early responders focuses attention on heterogeneity within obesity populations, highlighting that treatment effects are not uniform. These discussions point towards the future of obesity management that is more stratified, where treatmentselection is guided by predictive biomarkets, including early response.

Wegovy Pill

Novo Nordisk continued with pivotal insights being showcased at ECO2026, where they presented sub-analyses from the phase 3 OASIS 4 trial. The new findings show that 28.8% of patients were early responders to treatment, achieving an average of 13.2% weight loss after 4 months and 21.6% weight loss at the end of OASIS 4. The ORION indirect treatment comparison showed that Wegovy pill demonstrated significantly greater mean weight loss than orforglipron 36 mg, and orforglipron was associated with ~14 times higher odds of stopping medication due to gastrointestinal side effects ³.

These findings further strengthen the case for oral therapies within obesity treatment, demonstrating that substantial weight loss is achievable in pill form for a meaningful subset of patients. At the same time, the data highlight increasing differentiation within the oral landscape, with emerging variation in both efficacy and discontinuation profiles across agents. The ORION comparison further highlights tolerability as an important theme, particularly given higher discontinuation linked to gastrointestinal side effects. Together, these reinforce that beyond weight loss efficacy, convenience and tolerability are becoming increasingly important considerations.

Treating specific populations

One of the most important takeaways from ECO 2026 was the growing narrative that obesity is not a uniform condition, and that treatment needs to be adapted to specific populations. A prominent theme was obesity in the elderly, specifically sarcopenic obesity, a condition characterized by an intersection of excess body weight and age-related muscle loss. Data from Novo Nordisk’s REDEFINE 1 trial illustrated how this challenge can be addressed. CagriSema delivered substantial, fat-predominant weight loss while preserving muscle strength and physical function. At 68 weeks, around two thirds of the reduction was driven by fat mass, with the proportion of lean tissue increasing at higher levels of weight loss. Muscle strength was maintained and patient-reported physical function improved versus placebo ⁴.

These findings reflect a broader shift in how success is defined. ECO 2026 highlighted that preserving muscle and function is essential, particularly for older patients where frailty and mobility are real risks. Alongside age related considerations, gender emerged as another population shaping real world obesity care. A recurring observation across sessions was that a large proportion of current GLP-1 users are women, many of whom are pre , peri or post menopausal. At ECO 2026, this real world user profile helped explain why obesity treatment, women’s health (including menopausal status) and cardiovascular risk should be discussed together. Academic sessions highlighted growing interest in the combined impact of hormone replacement therapy (HRT) and GLP-1 treatment. HRT is already known to show cardiovascular benefits when appropriately prescribed around the time of menopause. The addition of effective weight loss and metabolic improvement from GLP-1s raises the prospect of complementary effects on cardiovascular outcomes in women.

These discussions signaled a clear shift. Obesity care is moving beyond a one size fits all approach, towards tailored strategies that reflect patient sub-populations.

Beyond BMI

Another theme running through ECO 2026 was continued movement away from BMI as the dominant framework for defining obesity and evaluating treatment success. While BMI remains widely used, it has limitations, and research showed that this was not always routinely documented, as demonstrated in the IMPACT-O study, leveraging IQVIA data ⁵. Sessions at ECO 2026 pointed towards a treat-to-target approach. Rather than focusing on percentage weight loss alone, discussions had moved towards targeting improvements in specific, clinically meaningful outcomes such as cardiometabolic risk, physical function, body composition and patient reported health status. Advanced imaging and body composition tools featured prominently throughout ECO 2026. Techniques that distinguish fat mass from lean mass are becoming more relevant for weight loss conversations. Waist to height ratio was highlighted as a more informative indicator than BMI, particularly for tracking changes over time and across diverse body types, because it reflects the accumulation (or loss) of visceral fat, which is the most harmful for metabolic dysfunction. This shift also implies a move away from percentage weight loss as the primary endpoint. ECO 2026 highlighted growing interest in more comprehensive outcome frameworks that integrate metabolic health, function and quality of life alongside weight change.

At the same time, the ECO 2026 underlined a more basic challenge. Findings from the IMPACT O study showed that BMI itself is inconsistently recorded in routine care. The proportion of patients with documented BMI ranged widely by country, from nearly 39% in the UK to around 5% in Germany and Australia ⁵.

A changing global policy backdrop

These scientific discussions took place against a shifting epidemiological context. A global progress report led by Imperial College London reported that the obesity rise is plateauing in developed nations and accelerating in developing nations ⁶. This does not suggest the obesity challenge is solved, but it hints at an inflection point where policies on prevention and management may be beginning to bend the curve- the time period studied was largely prior to the advent of widespread use of the modern obesity medications, adding the intriguing question, for future investigation, of what happens when the impact of extensive use of these medications can be evaluated.

Together, these themes point to a shift in obesity care, from short-term weight loss performance towards long-term health management. Maintenance of weight loss, a better recognition of the differing needs of different patient groups, for example, segmented by sex, age, ethnicity and experience of the weight loss and maintenance journey and broader outcome measures are increasingly defining how success in the prevention and management of obesity is understood. There will be continued important policy developments, trial readouts and launches in the remainder of 2026 and the run up to ECO 2027, to be held in Munich, to be followed.

Sources:

1. Lilly's Foundayo and lower-dose Zepbound helped people maintain weight loss after switching from higher doses of injectable incretin therapy in two late-phase trials; May 2026: https://investor.lilly.com/news-releases/news-release-details/lillys-foundayo-and-lower-dose-zepbound-helped-people-maintain

2. Novo Nordisk’s high-dose Wegovy touts near 28% weight loss in early responders; May 2026: https://www.clinicaltrialsarena.com/news/novo-nordisk-wegovy-high-dose-27-7-weight-loss-early-responders/

3. Wegovy® pill delivered 21.6% weight loss in early responders and doubled mobility improvement, according to new Novo Nordisk data at ECO2026; May 2026: https://www.biospace.com/press-releases/wegovy-pill-delivered-21-6-weight-loss-in-early-responders-and-doubled-mobility-improvement-according-to-new-novo-nordisk-data-at-eco2026

4. ECO 2026: REDEFINE-1 demonstrates CagriSema’s improvement in body composition, May 2026: https://www.yahoo.com/news/articles/eco-2026-redefine-1-demonstrates-145251328.html

5. Artime, E., Spaepen, E., Zimner-Rapuch, S. et al. Epidemiology Landscape and Impact of Overweight and Obesity in Adults: Multi-country Results from the IMPACT-O Study. Adv Ther 42, 5148–5163 (2025). https://doi.org/10.1007/s12325-025-03333-1

6. NCD Risk Factor Collaboration (NCD-RisC). Obesity rise plateaus in developed nations and accelerates in developing nations. Nature 653, 510–518 (2026). https://doi.org/10.1038/s41586-026-10383-0