Addressing the Persistent Increase and Inequities in Metabolically Unhealthy Obesity: Toward an Understanding of Clinical Obesity

Young Sang Lyu; Sang Yong Kim

doi:10.4093/dmj.2025.0306

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Editorial Addressing the Persistent Increase and Inequities in Metabolically Unhealthy Obesity: Toward an Understanding of Clinical Obesity: Young Sang Lyu, Sang Yong Kim; Diabetes & Metabolism Journal 2025;49(3):405-406.
DOI: https://doi.org/10.4093/dmj.2025.0306
Published online: May 1, 2025

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Department of Endocrinology and Metabolism, Chosun University Hospital, Chosun University College of Medicine, Gwangju, Korea

Corresponding author: Sang Yong Kim

Department of Endocrinology and Metabolism, Chosun University Hospital, Chosun University College of Medicine, 365 Pilmun-daero, Dong-gu, Gwangju 61453, Korea E-mail: diabetes@chosun.ac.kr

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Obesity was first recognized as a disease by the World Health Organization in 1948; since then, various countries and medical societies have officially classified it as a disease [1]. However, the debate over whether obesity should be considered an independent disease persists in both the medical community and society. One of the main reasons for this controversy is the uncertainty whether all individuals with obesity have increased risk of cardiovascular and metabolic diseases. Not all individuals with obesity experience the same obesity-related complications, and some maintain a relatively healthy metabolic state; this discrepancy has garnered increasing attention.

In this context, the concepts of metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO) have emerged [2,3]. MHO refers to individuals who meet the obesity criteria but do not exhibit metabolic abnormalities such as hyperglycemia, dyslipidemia, or hypertension. In contrast, MUO refers to individuals with obesity who also have one or more metabolic risk factors, typically associated with a higher risk of chronic diseases. This classification allows a more individualized approach that goes beyond using only body mass index (BMI) to assess health, considering the actual impact of body fat on bodily functions and health outcomes. This shift could provide a clearer clinical identity for obesity as a disease and, ultimately, lead to more individualized treatment strategies.

From this perspective, the recent study by Zeng et al. [4] offers crucial insights into the temporal trends of MUO among United States adults, using two decades of nationally representative cross-sectional National Health and Nutrition Examination Survey data (1999 to 2018). The data document a steady, linear increase in MUO prevalence over time, with persistent disparities across age, race/ethnicity, and income. Specifically, middle-aged adults (45 to 64 years), non-Hispanic Black individuals, and lower-income groups exhibited consistently higher MUO rates. These findings not only reaffirm the growing burden of MUO but also point to structural inequities in health risks and preventive care.

The most important finding of this study is that the age-adjusted percentage of MUO was consistently higher in adults aged 45 to 64 years than in the older population. This finding represents a different pattern from the previously observed increase in MUO among the elderly, suggesting that metabolic health issues may become more severe starting in middle adulthood [5]. As a result, programs or policies aimed at preventing MUO need to be actively implemented at the early stages across various age groups, including middle-aged adults. This study emphasizes the importance of MUO prevention and suggests that a tailored approach considering age, sex, and socioeconomic background is necessary.

Notably, this study was performed at a time when the medical understanding of obesity is evolving. The 2025 Lancet Commission on the definition and diagnosis of clinical obesity has proposed moving away from BMI-centric approaches and toward a functional classification of obesity [6]. This new framework distinguishes between preclinical obesity—defined as excess adiposity without current end-organ dysfunction— and clinical obesity, where adiposity begins to impair tissue, organ, or systemic function. In this context, MHO may conceptually align with preclinical obesity, while MUO shares characteristics of clinical obesity, including the presence of metabolic dysfunctions that predict or reflect organ impairment. Thus, the observed increase in MUO prevalence suggests not just a quantitative increase in obesity but a qualitative shift toward clinical illness.

The public health implications of these findings are 2-fold. First, universal early screening for metabolic dysfunction in individuals with obesity is crucial. Second, policy interventions must prioritize health equity by ensuring access to preventive services, healthy environments, and treatment options—especially for structurally disadvantaged populations.

Addressing the increasing prevalence and inequities of MUO is essential not only for improving individual health outcomes but also for advancing public health initiatives that promote equity, early intervention, and more effective, personalized care strategies for all populations. With continuing discussions on the disease-oriented approach to clinical obesity, as proposed by the Lancet Commission, there is a growing need to further refine obesity phenotypes and pursue more individualized approaches. Additional research is needed on the diagnosis of obesity phenotypes or clinical obesity, as well as on personalized treatments and prognoses.

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CONFLICTS OF INTEREST

Sang Yong Kim has been an associate editor of the Diabetes & Metabolism Journal since 2022. He was not involved in the review process of this article. Otherwise, there was no conflict of interest.

REFERENCES

1. James WP. WHO recognition of the global obesity epidemic. Int J Obes (Lond) 2008;32 Suppl 7:S120-6.Article PubMed PDF
2. Iacobini C, Pugliese G, Blasetti Fantauzzi C, Federici M, Menini S. Metabolically healthy versus metabolically unhealthy obesity. Metabolism 2019;92:51-60.Article PubMed
3. Bluher M. Metabolically healthy obesity. Endocr Rev 2020;41:bnaa004.PubMed PMC
4. Zeng W, Zhou W, Pu J, Li J, Hu X, Yao Y, et al. Trends in metabolically unhealthy obesity by age, sex, race/ethnicity, and income among United States adults, 1999 to 2018. Diabetes Metab J 2025;49:475-84.Article PDF
5. Liu J, Zhang Y, Lavie CJ, Moran AE. Trends in metabolic phenotypes according to body mass index among US adults, 1999-2018. Mayo Clin Proc 2022;97:1664-79.Article PubMed
6. Rubino F, Cummings DE, Eckel RH, Cohen RV, Wilding JP, Brown WA, et al. Definition and diagnostic criteria of clinical obesity. Lancet Diabetes Endocrinol 2025;13:221-62.PubMed

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Addressing the Persistent Increase and Inequities in Metabolically Unhealthy Obesity: Toward an Understanding of Clinical Obesity

Diabetes Metab J. 2025;49(3):405-406. Published online May 1, 2025

DOI: https://doi.org/10.4093/dmj.2025.0306

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Addressing the Persistent Increase and Inequities in Metabolically Unhealthy Obesity: Toward an Understanding of Clinical Obesity

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Lyu YS, Kim SY. Addressing the Persistent Increase and Inequities in Metabolically Unhealthy Obesity: Toward an Understanding of Clinical Obesity. Diabetes Metab J. 2025;49(3):405-406.

DOI: https://doi.org/10.4093/dmj.2025.0306.

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