Most Bariatric Surgery Candidates Meet New Clinical Obesity Criteria

Nearly 3 in 4 adults undergoing metabolic bariatric surgery (MBS) at 4 international centers met criteria for clinical obesity under a new disease-based framework, despite body mass index (BMI) levels similar to patients without obesity-related organ dysfunction, according to a study published in JAMA Network Open.¹

The framework comes from the Lancet Diabetes & Endocrinology Commission, which in January 2025 proposed separating clinical obesity, a chronic illness in which excess adiposity causes organ dysfunction or limits daily activities, from preclinical obesity, in which organ function is preserved but future health risk is elevated.² Francesco Rubino, MD, of King's College London, who led the commission, is the corresponding author of the new study.

Investigators retrospectively classified 2316 adults who underwent primary gastric bypass or sleeve gastrectomy between 2014 and 2025 at high-volume centers in London, Barcelona, Lille, and São Paulo, using diagnoses, laboratory values, medication use, and documented functional limitations. Patient-level data were not pooled, so comparisons were made only within each cohort.¹ The authors noted that selection for MBS still rests largely on BMI thresholds rather than clinical conditions.

Clinical Obesity Was the Majority at Every Center

Overall, 1709 patients (73.8%) had clinical obesity and 607 (26.2%) had preclinical obesity, with clinical obesity ranging from 62.7% of the Brazilian cohort to 79.3% of the UK cohort. Within each center, mean BMI did not differ significantly between groups, and the distribution of patients across BMI categories (<40, 40-49, and ≥50) was comparable.

Among patients with clinical obesity, the most common qualifying dysfunctions were hypertension (57.6%), metabolic dysfunction (44.1%), sleep apnea requiring continuous positive airway pressure (40.1%), and functional or musculoskeletal limitation (20.1%), though prevalence varied widely by site. Patients with clinical obesity were older than those with preclinical obesity in every cohort (mean age range, 45.6-48.9 vs 34.7-40.0 years; all P < .001).

Higher Baseline Risk and Modestly Smaller Weight Loss With Clinical Obesity

Clinical obesity was associated with higher American Society of Anesthesiologists classifications in all 4 cohorts and with higher Charlson Comorbidity Index and Framingham cardiovascular risk scores in every cohort that reported those measures (3 cohorts each). In the French cohort, for example, the median Framingham score was 8.00 with clinical obesity vs 2.00 with preclinical obesity (P < .001).

Major 30-day complications (Clavien-Dindo grade ≥3) were more frequent with clinical obesity in the French cohort (4.0% vs 1.1%; P = .04), while differences in the UK and Spanish cohorts were small and not significant; complication data were unavailable for Brazil. Patients with clinical obesity also lost modestly less weight after surgery, by about 2 to 4 percentage points, with significant differences in the Spanish, French, and Brazilian cohorts at 12 months and in the French and Brazilian cohorts at 24 months. The UK cohort showed no significant difference at either time point.

Implications for Prioritization and Value

The authors suggested that health systems with limited surgical capacity could use the distinction to prioritize patients with demonstrable obesity-related dysfunction. As obesity pharmacotherapy expands, surgery could serve as a second-line, risk-reduction option in preclinical obesity but as a first-line or early treatment for many patients with clinical obesity, they wrote, adding that outcomes in clinical obesity should be measured beyond weight loss.

The authors also suggested the economics may differ by disease status. Surgery in clinical obesity may pay off sooner through fewer complications, less medication use, and fewer hospitalizations, they wrote, while surgery in preclinical obesity should be evaluated as a preventive intervention with a longer time horizon and potentially different cost-effectiveness thresholds. The study did not analyze costs, and the authors called for future health economic analyses that separate the 2 groups.

Because the study was retrospective, it could not confirm that each dysfunction was caused by obesity, which the authors said may have led to overestimation of clinical obesity. Some criteria relied on pragmatic proxies, and several authors reported grants or fees from bariatric device and obesity drug manufacturers.

“These findings support implementation of the new definitions of clinical and preclinical obesity in surgical practice to improve patient selection, prioritization, and alignment of treatment goals with clinical need,” the authors wrote. “Metabolic bariatric surgical services should systematically assess obesity-related organ dysfunction; report the prevalence of clinical and preclinical obesity; and interpret safety, efficacy, and cost-effectiveness within the appropriate clinical context, distinguishing when surgery is used for treatment of established disease vs risk reduction.”

References

1. Cremona S, Cohen RV, Pattou F, et al. New obesity definition and clinical obesity prevalence for global metabolic bariatric surgery. JAMA Netw Open. 2026;9(8):e2628395. doi:10.1001/jamanetworkopen.2026.28395
2. Rubino F, Cummings DE, Eckel RH, et al. Definition and diagnostic criteria of clinical obesity. Lancet Diabetes Endocrinol. 2025;13(3):221-262. doi:10.1016/S2213-8587(24)00316-4