New obesity framework may reclassify over half of overweight individuals as people with obesity

1. In this cross-sectional study, a new obesity framework from the European Association for the Study of Obesity reclassified an additional nearly one-fifth of the United States population as obese.

2. The newly classified people with obesity had a higher mortality risk compared with adults with normal weight and no comorbidities, although they had similar risk to adults with normal weight and comorbidities.

Evidence Rating Level: 3 (Average)

Study Rundown: The European Association for the Study of Obesity (EASO) recently released a new framework defining obesity either as body mass index (BMI) ≥30 kg/m² or as BMI between 25 and 30 kg/m² with an elevated waist-to-height ratio (WtHR) and the presence of any medical, functional, or psychological complications. This study aimed to compare the population of individuals with obesity according to the existing definition and the EASO definition, and examine the complications prevalent within the newly defined subset. Among a sample of American adults, over one-third of the population was considered PWO per BMI alone; the new definition led to almost an additional twenty percent of the population being reclassified as PWO. Of the one-third of individuals who were considered overweight by BMI alone, over half were PWO; these individuals were generally older compared to those who were considered overweight or PWO per BMI alone. The newly classified PWO were more likely to have comorbidities, with the most common being hypertension and arthritis. Among patients considered overweight who were not reclassified as PWO, the majority met the WtHR ratio but did not meet the morbidity requirement. The newly reclassified PWO had a higher mortality compared with individuals with normal weight and no comorbidities, but similar mortality to that of individuals with normal weight who had comorbidities. The generalizability of this study was limited by potential confounding, the cross-sectional design, and missing data. Overall, this study clarified how the new EASO framework affected the apparent population makeup of PWO.

Click to read the study in AIM

Relevant Reading: A new framework for the diagnosis, staging and management of obesity in adults

In-Depth [cross-sectional study]: This study aimed to determine how the new EASO framework affected the population distribution of individuals with overweight and obesity. The patient population was sampled from the National Health and Nutrition Examination Survey (NHANES), made up of individuals aged between 18 and 79 years.  The EASO framework defined normal as BMI between 18.5 and 25 kg/m², overweight as BMI between 25 and 30 kg/m² with WtHR <0.5 or without comorbidities, and obesity as BMI ≥30 kg/m² or between 25 and 30 kg/m² with WtHR ≥0.5 and at least 1 comorbidity. After applying exclusion criteria, the final sample was 44,030 individuals. Based on BMI alone, 31.3% of the study population was considered normal weight, 33.3% overweight, and 35.4% PWO. Applying the EASO framework caused 18.8% of participants (56.4% of people with overweight) to be reclassified as PWO, meaning that 54.2% of participants were now considered PWO. More men (21.9%) than women (15.6%) were newly classified as PWO; the newly classified PWO were older (51.3 years; standard deviation [SD], 14.5) than persons defined as overweight (36.5 years; SD, 12.2) or PWO (45.4 years; SD, 15.0) based on BMI alone. Among the newly classified PWO, 57.5% had at least 1 comorbidity and 42.5% had more than 1, compared with 34.3% and 38.7%, respectively, among PWO based on BMI alone. Compared with individuals with normal weight and no comorbidities, both the newly classified PWO (adjusted HR, 1.50 [95% CI, 1.20 to 1.88]) and individuals with BMI ≥30 kg/m² (adjusted HR, 1.82 [95% CI, 1.46 to 2.27]) had higher mortality risk, which was not significantly different from the mortality risk among individuals with normal weight and comorbidities (HR, 1.74 [95% CI, 1.34 to 2.22]). Both the newly classified PWO (adjusted HR, 1.77 [95% CI, 1.36 to 2.32]) and individuals with BMI ≥30 kg/m² (adjusted HR, 1.76 [95% CI, 1.36 to 2.29]) had increased mortality risk compared with individuals who remained classified as overweight. These effects were consistent across subgroup analyses.

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