TOPLINE

The prevalence of obesity classes 4 and 5 (BMI ≥ 50 kg/m2) in US adults increased by more than 250% from 2000 to 2023. Adults with extremely severe obesity had odds ratios for metabolic comorbidities and mortality compared with those without obesity.

METHODOLOGY

• Researchers analyzed data from National Health and Nutrition Examination Surveys from 2000 through 2023 involving 54,793 adults (median age, 40 years; 47.7% men; median BMI, 27.8 kg/m2) in the United States. Mortality data were available for 43,454 adults, with follow-up extending through 2018.
• Obesity class 4 was defined as BMI ≥ 50 kg/m2 to < 60 kg/m2, and class 5 as BMI ≥ 60 kg/m2.
• Metabolic dysfunction–associated steatotic liver disease (MASLD) was defined by hepatic steatosis (controlled attenuation parameter ≥ 302 dB/m) plus at least one cardiometabolic criterion.
• Analysis included assessment of metabolic syndrome, prediabetes, type 2 diabetes (T2D), insulin resistance, and hepatic fibrosis across obesity classes.

TAKEAWAY

• The prevalence of class 4 obesity increased by 255.6% (0.6% to 2.2%; P < .001) and that of class 5 obesity rose by 246.7% (0.2% to 0.5%; P < .001) between 2000 and 2023.
• Extremely severe obesity (classes 4–5) was associated with significantly higher prevalence of MASLD (75.5% vs 11.7% in those without obesity and 47.9% in classes 1–3; all P < .001). Obesity class 5 demonstrated the highest median liver stiffness (15.3 kPa vs 4.6 kPa without obesity) and highest prevalence of hepatic fibrosis stage 4 (55.2% vs 1.1% without obesity; P < .001).
• The prevalence of insulin resistance and severe insulin resistance was significantly higher in obesity classes 4–5 than without obesity (97.3% and 14.5% vs 31.2% and 0.7%; both P < .001). Metabolic syndrome prevalence was highest in class 5 obesity (89.7% vs 38.1% in those without obesity; P < .001).
• Obesity classes 4 and 5 were associated with a 10-year mortality compared with no obesity (hazard ratio [HR], 2.2; P < .001) and obesity classes 1-3 (HR, 1.8; P < .001).

IN PRACTICE

"This study demonstrates that extremely severe obesity is increasing in prevalence and is associated with significant metabolic complications and a high risk of mortality," the authors of the study wrote. "Targeted public health interventions are hence required to support and help this patient population."

SOURCE

The study was led by Katelynn Tran, University of California San Diego, La Jolla. It was published online on July 22 in Obesity Science & Practice.

LIMITATIONS

The study used liver imaging rather than biopsy to diagnose MASLD. 

DISCLOSURES

The study was supported by grants from the National Institutes of Health, University of California San Diego Altman Clinical and Translational Research Institute, and the American Association for the Study of Liver Diseases.  The authors reported having no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.