Clinical Obesity Common in Bariatric Surgery Candidates
Key Takeaways
- Among adults undergoing primary metabolic bariatric surgery at 4 high-volume tertiary centers in the UK, Spain, France, and Brazil, most were classified as having clinical obesity and a substantial minority as having preclinical obesity.
- Clinical obesity prevalence ranged from 62.7% in Brazil to 79.3% in the UK, although the authors noted that the UK and Brazilian datasets came from audit databases rather than complete institutional registries, limiting how representative those center-specific estimates may be.
- Similar body mass index (BMI) levels and BMI category distributions did not correspond to similar disease burden, as clinical obesity was associated with older age and higher baseline risk markers within each cohort.
- Major complications were significantly higher only in the French cohort, and lower postoperative weight loss generally favored the preclinical-obesity groups across several cohorts.
In a retrospective multicenter cross-sectional audit reported by Cremona et al in JAMA Network Open, investigators used prospectively maintained clinical databases and registries from King's College Hospital in London, Hospital del Mar in Barcelona, Centre Hospitalier Universitaire de Lille, and Hospital Alemão Oswaldo Cruz in São Paulo. The cohort included 2316 adults undergoing primary laparoscopic Roux-en-Y gastric bypass or laparoscopic sleeve gastrectomy from January 1, 2014, through December 31, 2025, with revisional procedures, multiple bariatric operations in the same year, and cases lacking formal obesity-related disease assessment excluded.
Investigators retrospectively operationalized the Lancet Commission framework across 18 adiposity-related organ dysfunction domains using diagnoses, laboratory measures, imaging, specialist follow-up, medication use, and documented functional limitations. The primary outcome was prevalence of clinical obesity; secondary outcomes included BMI pattern, American Society of Anesthesiologists (ASA) class, Charlson Comorbidity Index (CCI), Framingham risk, perioperative major complications, and postoperative weight loss. Because patient-level data were not shared across centers, analyses were performed within cohorts and only aggregated results were compared.
Among 2316 patients, 1709 (73.8%) met criteria for clinical obesity and 607 (26.2%) for preclinical obesity. Clinical obesity predominated in every cohort, ranging from 62.7% in Brazil to 79.3% in the UK, although the authors noted that the UK and Brazilian datasets came from audit databases rather than complete institutional registries, limiting how representative those center-specific estimates may be. Within each center, BMI levels and BMI category distributions were similar between phenotypes, yet patients with clinical obesity were older and had higher ASA class across cohorts, with higher CCI and Framingham risk where those measures were available.
Within the clinical-obesity phenotype, the most common dysfunction domains were hypertension, metabolic dysfunction, functional or musculoskeletal limitation, and sleep apnea requiring continuous positive airway pressure (CPAP), although the mix varied substantially across centers. Major 30-day postoperative complications were more frequent in the French cohort at 4% versus 1.1% (P=.04), while UK and Spanish cohorts were not significantly different and Brazilian complication data were unavailable. Postoperative weight loss showed the same general pattern, exemplified by the French 24-month comparison of 29.6% versus 33.6% (P<.001), with similar lower-weight-loss findings for clinical obesity at other assessed time points in Spain, France, and Brazil.
The authors said the retrospective audit drew on heterogeneous routine datasets that were not created for this framework, so organ dysfunction often required pragmatic adjudication, grouped categories, or proxy measures. Upper-airway dysfunction relied on documented sleep apnea treated with CPAP, and liver dysfunction depended on center-specific evidence for steatohepatitis with fibrosis or findings suggestive of metabolic dysfunction-associated steatohepatitis (MASH), with histology available in France but not uniformly elsewhere. The authors also noted that obesity could not be established as the definitive cause of each dysfunction, which may have inflated clinical-obesity prevalence, and that patient-level data were not pooled across centers; CCI was unavailable in France, Framingham risk in the UK, and perioperative complication data in Brazil.
The authors concluded that clinical obesity was the predominant phenotype across these metabolic bariatric surgery cohorts, while a meaningful minority of patients still met criteria for preclinical obesity despite similar BMI distributions. In their interpretation, the classification helped characterize baseline disease burden, operative risk, and postoperative trajectory within bariatric surgery cohorts rather than allowing severity to be inferred from BMI alone.
Clinician Questions
How was clinical obesity classified in bariatric surgery candidates under the Lancet Commission framework?
Investigators retrospectively applied the framework across 18 adiposity-related organ dysfunction domains using documented diagnoses, laboratory measures, imaging, specialist follow-up, medication use, and functional limitations. In this scheme, clinical obesity denotes excess adiposity with organ dysfunction or impaired function, whereas preclinical obesity denotes excess adiposity with preserved function.
Why were center-to-center comparisons not pooled in this bariatric surgery obesity analysis?
Each institution kept patient-level data locally, so analyses were performed within cohorts under a harmonized protocol and only aggregated findings were shared. That makes the UK, Spain, France, and Brazil results strongest as within-center comparisons rather than as a single pooled patient-level analysis.
What counted as upper airway or liver dysfunction when investigators retrospectively diagnosed clinical obesity?
For upper-airway dysfunction, investigators pragmatically used documented CPAP-treated sleep apnea as a proxy. For liver dysfunction, fibrosis was histologically confirmed in France, while other centers relied on documented MASH, persistent abnormal liver enzymes, or specialist follow-up/imaging suggestive of steatohepatitis.
How far do these findings extend beyond bariatric surgery programs?
These findings are most applicable to adults undergoing primary laparoscopic Roux-en-Y gastric bypass or sleeve gastrectomy at four high-volume tertiary centers in the UK, Spain, France, and Brazil. The authors noted that nonsurgical populations may have lower clinical-obesity prevalence and called for prospective studies with standardized assessments before broader estimates are assumed.