Prevalence of obesity: comparison of traditional and new classification methods in a Swiss population-based study (2005-2024)

Nehme, M., Mettraux, C., Chevalier, C., Dumont, R., Schrempft, S., Farpour-Lambert, N., Guessous, I.

Obesity prevalence: comparison of traditional and new classification approaches in a Swiss population-based study (2005-2024).Int J Obes(2026). https://doi.org/10.1038/s41366-026-02076-5

Summary :

Objectives: The aim of this study was to compare the prevalence of obesity according to the traditional classification based on BMI alone and the new classification proposed in 2025 by the "Lancet Diabetes & Endocrinology" Commission. This new approach combines BMI with other simple body measurements, such as waist circumference or waist-to-hip and waist-to-height ratios. The study also examines the links between these classifications and cardiovascular and metabolic diseases.

Methods: The Bus Santé study is a cross-sectional study conducted in Geneva, Switzerland. The analysis covers data collected between 2005 and 2024, including 14,658 people (mean age: 48.2 years; 51.4% women; participation rate: 61%). Obesity was defined either by BMI alone or using combinations including other body measurements. Associations with diabetes, hypertension and dyslipidaemia (lipid disorders) were analysed using logistic regression and ROC curves (a measure of the ability to correctly identify people at risk).

Results: The prevalence of obesity varied widely depending on the definition used, ranging from 13.1% with BMI alone to 39.9% with certain combinations of measures. The new classifications identify more people at risk, with differences according to age and sex. They also perform better in detecting associated diseases. For example, the combination of BMI + waist-hip ratio is most strongly associated with diabetes (aOR: 4.61 [3.87-5.47]), while waist-hip ratio + waist-height ratio shows the strongest association with dyslipidaemia (aOR: 1.95 [1.75-2.16]). Socio-economic differences were also observed: people with a primary education were more often classified as obese using these new approaches.

Discussion: The addition of simple measures such as waist circumference to BMI considerably improves the detection of obesity and of people at risk of cardiovascular and metabolic disease. These new definitions appear to be particularly useful in clinical practice, especially for detecting risk profiles that would not be identified by BMI alone, such as the elderly, those with abdominal obesity without a high BMI, or socio-economically disadvantaged populations. These measurements are easy to perform in general practice and provide an inexpensive tool for early detection of people on the obesity spectrum, enabling timely therapeutic or lifestyle interventions to prevent complications.

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This text was automatically translated from French using artificial intelligence