Neck Circumference May Signal Hidden Metabolic Risk in People with Obesity

A thick neck might seem like an odd place to look for the earliest warning signs of diabetes and heart disease, but a new study from Malaysia suggests that the tape measure may belong there after all. Researchers at Universiti Malaya Medical Centre examined nearly 300 healthcare workers who were carrying excess weight yet considered themselves healthy, and they found that metabolic disturbance was far more common than anyone expected. Among people with a body mass index of 30 or above, more than 85 percent already showed at least one metabolic abnormality, despite having no diagnosed disease. The findings, published in BMC Endocrine Disorders, add to a growing body of evidence that the so-called metabolically healthy obesity phenotype is rarer than it appears, and that simple bedside measurements could help identify who is quietly slipping toward cardiometabolic disease.

The concept of metabolically healthy obesity has long divided the field. Some individuals with elevated body mass index maintain normal blood pressure, glucose metabolism and blood lipids, while others with the same degree of excess weight develop hypertension, dysglycemia and dyslipidemia. Whether the healthy phenotype is a stable state or merely an early stage on the road to disease remains contested, and the answer matters enormously for screening and prevention. Asian populations complicate the picture further, because they develop obesity-related complications at lower body mass index thresholds than European populations, which is why the study used the Asian-specific cutoff of 23 kilograms per square meter rather than the World Health Organization’s global threshold of 25. Healthcare workers, paradoxically, show higher rates of obesity than the general population despite their medical knowledge, making them an instructive group in which to study the transition from apparent health to metabolic dysfunction.

The research team recruited 297 employees of an urban Malaysian academic medical centre through voluntary convenience sampling. Eligible participants had a body mass index of at least 23 kilograms per square meter and no known cardiometabolic disease, meaning the cohort represented people who would typically pass an occupational health check without raising alarms. Each participant underwent a detailed anthropometric assessment, including neck circumference, waist circumference and hip circumference, alongside bioelectrical impedance analysis, a technique that estimates body composition by measuring how the body resists a weak electrical current. Because fat-free mass, which is largely muscle and water, conducts electricity well while fat resists it, the method can partition body weight into fat mass and fat-free mass with reasonable accuracy for population studies. Blood pressure, fasting glucose and lipid profiles completed the picture, allowing the researchers to classify each person as metabolically healthy or unhealthy.

The classification criteria were strict. Metabolically healthy overweight or obesity, abbreviated MHOO, required the complete absence of any metabolic abnormality: no dysglycemia, no elevated blood pressure and no dyslipidemia. Anyone with even one of these features was classified as metabolically unhealthy overweight or obesity, or MUOO. By this standard, only 100 of the 297 participants, or 33.67 percent, qualified as metabolically healthy. The proportion shrank as body mass index rose. At the obesity threshold of 30 kilograms per square meter, 85.32 percent of participants were metabolically unhealthy. Elevated blood pressure emerged as the predominant abnormality, a finding with particular relevance for Asian populations, in which hypertension-related cardiovascular disease often develops at lower body mass indices than in other groups.

When the researchers compared the two phenotypes, the metabolically unhealthy group carried both more fat mass and more fat-free mass than their healthier counterparts. That second observation is the more intriguing one, because fat-free mass expansion is often assumed to be benign or even protective. The correlation analysis revealed a clear division of labour among the simple measurements. Body mass index, waist circumference, hip circumference and waist-to-height ratio all correlated strongly with fat mass, with Spearman coefficients ranging from 0.75 to 0.93, confirming that these indices essentially track how much fat a person carries. Neck circumference and waist-to-hip ratio, by contrast, correlated better with fat-free mass, with coefficients of 0.68 and 0.41 respectively. Neck circumference also showed a moderate correlation of 0.44 with the triglyceride-glucose index, an insulin-resistance marker calculated from fasting triglycerides and glucose that has gained popularity as a cheap surrogate for more invasive metabolic testing.

To determine which measurements independently predicted metabolic status, the team built multivariable logistic regression models adjusted for sociodemographic factors, body composition metrics and the other anthropometric indices. After all adjustments, only neck circumference retained a modest but statistically significant association with metabolically unhealthy status, with an adjusted odds ratio of 1.15 per unit increase and a 95 percent confidence interval of 1.01 to 1.32. The association weakened when the triglyceride-glucose index was added to the model, a pattern that suggests neck circumference may act partly through insulin resistance rather than as an independent risk marker. In other words, a thicker neck may not itself cause metabolic disease, but it appears to flag the same underlying physiology that drives it.

The exploratory mediation analyses pushed this interpretation further. Using parallel mediation models, the researchers tested whether fat mass and fat-free mass explained the link between anthropometric measurements and metabolic risk. Both expansions of fat and lean mass appeared to mediate the association, but the pattern of correlations hinted at something more specific: a predilection for upper-body expansion of fat-free mass may be linked with metabolically unhealthy obesity. This is where the neck measurement earns its place at the table. The neck houses not only subcutaneous fat but also substantial muscle and other lean tissue, and upper-body fat depots are metabolically more active and more harmful than those in the lower body. Fat stored in and around the trunk and upper body drains directly into the portal circulation, flooding the liver with free fatty acids and promoting insulin resistance, whereas gluteofemoral fat is comparatively protective. If neck circumference captures upper-body lean tissue expansion along with fat, it may serve as a composite marker of a metabolically adverse body composition pattern that waist measurements alone miss.

The technical details matter for anyone hoping to translate these findings into practice. Bioelectrical impedance, while convenient and inexpensive, estimates rather than directly measures body composition, and its accuracy varies with hydration status and body geometry. Computed tomography and magnetic resonance imaging remain the gold standards for quantifying visceral fat and regional muscle mass, but they are impractical for population screening. The triglyceride-glucose index, like neck circumference, is attractive precisely because it costs almost nothing to obtain. The study’s cross-sectional design also imposes limits: it captures a single moment in time, so it cannot establish whether neck circumference predicts the future development of diabetes or cardiovascular disease, only that it is associated with current metabolic status. The authors themselves describe the mediation findings as exploratory and call for confirmation in larger cohorts, and the convenience sampling of healthcare workers at a single urban centre may limit generalizability, particularly since healthcare workers differ from the general population in activity levels, health literacy and access to care.

Even with those caveats, the study carries a message that resonates well beyond Malaysian hospitals. Metabolic disturbance is common among people who consider themselves healthy and who would rarely be screened aggressively, because they carry excess weight but no diagnosis. Elevated blood pressure, the most frequent abnormality in this cohort, is both silent and treatable, which makes finding it early genuinely consequential. The study also challenges the comfortable narrative that muscle mass is always protective. Fat-free mass expansion, at least when concentrated in the upper body, may travel alongside insulin resistance rather than against it, a nuance that could reshape how clinicians interpret body composition data from impedance scales increasingly found in gyms and clinics.

For now, the practical takeaway is modest but concrete. A tape measure around the neck, a measurement that takes seconds and requires no laboratory, may help clinicians identify patients with overweight or obesity who deserve closer metabolic scrutiny, especially in Asian populations where risk arrives at lower body mass indices. The researchers, led by Quan-Hziung Lim and Lee-Ling Lim of Universiti Malaya, published their work open access so that other teams can test the hypothesis in larger and more diverse cohorts. If the neck circumference signal survives that scrutiny, one of medicine’s simplest instruments may gain a new role in the fight against two of its most burdensome diseases. Until then, the study stands as a reminder that the body’s metabolic story is written in more places than the waistline, and that some of those places are hiding in plain sight, just below the chin.

Subject of Research: Anthropometric and body composition determinants of metabolically healthy versus unhealthy overweight/obesity in Malaysian healthcare workers

Article Title: Anthropometric and body composition determinants of metabolically healthy and unhealthy overweight/obesity: an analysis among Malaysian healthcare workers

Article References: Lim, Q.-H., Packrisamy, D., Ong, J. S., Kang, M. L., Hee, N. K. Y., Sarvanandan, T., Ooi, Y. G., Khoo, J. K., Ratnasingam, J., Vethakkan, S. R., & Lim, L.-L. (2026). Anthropometric and body composition determinants of metabolically healthy and unhealthy overweight/obesity: an analysis among Malaysian healthcare workers. BMC Endocrine Disorders. https://doi.org/10.1186/s12902-026-02530-5

Image Credits: AI Generated

DOI: 10.1186/s12902-026-02530-5

Keywords: obesity, metabolic syndrome, neck circumference, body composition, anthropometry, insulin resistance, hypertension, bioelectrical impedance, fat-free mass, triglyceride-glucose index, Malaysia, healthcare workers