Undiagnosed Diabetes in Metabolically Unhealthy Normal Weight Adults: A Cross-Sectional Analysis of National Health and Nutrition Examination Survey Cycle 2017–2020 in the United States

TL;DR

This study finds that normal-weight adults with metabolic issues are more likely to have undiagnosed diabetes, especially Asians, suggesting BMI alone is not enough for screening.

Contribution

The study highlights the limitations of using BMI alone for diabetes screening and identifies significant racial disparities in undiagnosed diabetes prevalence.

Findings

Undiagnosed diabetes prevalence was 4.84% in metabolically unhealthy normal weight adults versus 1.28% in metabolically healthy ones.

Asian adults had a 6.10 times higher risk of undiagnosed diabetes compared to White adults, independent of metabolic phenotype.

Age and race were significant predictors of undiagnosed diabetes in normal-weight individuals.

Abstract

Background/Objectives: Although body mass index (BMI) is a conventional screening tool for type 2 diabetes mellitus (T2D), its reliability as a sole indicator of metabolic health is controversial, and the metabolic profile of a subset of individuals with normal BMI is indicative of obesity-related complications. This study aimed to estimate the prevalence and predictors of undiagnosed diabetes among Metabolically Unhealthy Normal Weight (MUNW) adults. Methods: Data from the National Health and Nutrition Examination Survey (NHANES) 2017–March 2020 were analyzed. Normal weight adults (BMI 18.5–24.9 kg/m2) were categorized into Metabolically Healthy (MHNW) and Unhealthy (MUNW) phenotypes based on the presence of ≥2 metabolic risk factors, including elevated blood pressure, triglycerides, waist circumference, or low HDL cholesterol. The primary outcome was undiagnosed diabetes, defined as HbA1c ≥ 6.5% or Fasting Plasma Glucose ≥ 126 mg/dL. Results: The study population represented approximately 60 million US adults. The prevalence of undiagnosed diabetes was nearly four times higher in the MUNW group (4.84%) compared to the MHNW group (1.28%). In multivariable logistic regression analysis, age and race emerged as significant predictors. Notably, Asian adults exhibited a significantly higher risk of undiagnosed diabetes (OR 6.10; 95% CI: 1.32–28.2) compared to White adults, independent of metabolic phenotype. Conclusions: Reliance solely on BMI may overlook undiagnosed diabetes in normal-weight adults, particularly those with metabolic clustering or of Asian descent. These findings underscore the importance of multidimensional risk assessment integration into preventive care, optimizing clinical management.

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