ADOPTING new clinical criteria for defining obesity, requiring the presence of additional health conditions such as diabetes, hypertension, or raised cholesterol, would dramatically reduce reported obesity prevalence worldwide, but could risk overlooking many at-risk individuals who would no longer be classified as obese under surveillance systems.
Obesity is a major public health challenge with rising prevalence globally, often identified using the body mass index (BMI) threshold of 30 kg/m². However, BMI alone does not reflect the full metabolic or functional health burden associated with excess weight. In recent years, proposals have called for a new, more stringent definition that incorporates both BMI and evidence of metabolic complications such as diabetes, hypertension, or hypercholesterolaemia. This has sparked debate about how changing the definition might impact disease monitoring, public health interventions, and individual awareness of risk.
In the first multinational study to evaluate this impact, researchers analysed health survey data from 142,250 adults across 56 countries, comparing standard BMI-based obesity prevalence with that calculated using the proposed clinical criteria. Under the new definition—which combines BMI thresholds with waist-to-height ratio or evidence of major metabolic disease—the prevalence of clinical obesity fell sharply. For instance, in Malawi, the prevalence among men dropped from 0.7% (using BMI alone) to 0.2% (relative change: -68%), while among women the drop was from 5.6% to 2.6% (relative change: -53%). Across all settings, most countries showed clinical obesity rates under 10% for both men and women, with the strictest reductions seen in sub-Saharan Africa. The new criteria produced marked variability by country and gender, raising concerns about the comparability and equity of future surveillance if adopted.
While defining obesity more tightly aligns diagnosis with existing metabolic risk, the study’s authors caution that a substantial drop in reported prevalence could lead to health services missing individuals who remain at elevated long-term risk but do not yet present overt comorbidities. In practical terms, individuals with a high BMI but no diagnosed metabolic disease would fall outside the revised definition and may receive less preventive support. For clinical practice, it is vital that early intervention and healthy lifestyle advice remain available to all those at elevated risk, regardless of evolving definitions. Future research and policy discussions should weigh the merits of more targeted definitions against the broader need for effective prevention, public awareness, and meaningful comparisons over time.
Reference
Carrillo-Larco RM et al. Prevalence of pre-clinical and clinical obesity in adults: Pooled analysis of 56 population-based national health surveys. PLOS Global Public Health. 2025;5(7):e0004838.
