World Obesity Day: From Metabolic Risk to Measurable Reality

The Healthy Ireland Survey 2024 captured the health profile of 7,398 people aged 15 and over across Ireland between October 2023 and April 2024. It found that 63% of men and 50% of women reported living with overweight or obesity (1).

These figures are based on self-reported weight. Given the stigma and tendency to underestimate, the true prevalence is likely even higher.

On March 4, World Obesity Day reminds us that obesity is more than a public health statistic, it is a progressive metabolic condition reshaping the workload and responsibility of hospital laboratories worldwide.

Obesity is estimated to account for 80–85% of type 2 diabetes cases (2), and type 2 diabetes itself represents more than 90% of all diabetes diagnoses (3). But while obesity develops gradually, type 2 diabetes often becomes visible to the healthcare system through a single laboratory marker: HbA1c.

Obesity and the Biochemistry of Insulin Resistance

From a biochemical perspective, the pathway is clear. Excess adiposity, particularly visceral fat, drives systemic inflammation and elevated free fatty acids, leading to progressive insulin resistance (4).
As compensation fails, β-cell dysfunction develops, and metabolic stress advances to chronic hyperglycemia (5).
But hyperglycemia is not merely physiological – it is measurable. HbA1c quantifies that cumulative glycemic burden over time.

HbA1c: More Than a Number

Glycated hemoglobin reflects the attachment of glucose to the β-chain of hemoglobin A (6). Due to erythrocytes circulating for approximately 120 days, HbA1c provides an integrated measure of glycemic exposure over the preceding 2-3 months (7).

Clinically, it serves two critical roles:

• Diagnosis (≥48 mmol/mol or 6.5%)
• Longitudinal monitoring of glycemic control

Unlike fasting plasma glucose, HbA1c does not fluctuate with acute stress or short-term dietary variation (8). It reflects sustained metabolic imbalance, precisely the kind driven by obesity-related insulin resistance.
For the clinician, it guides treatment decisions.
For the patient, it predicts risk of microvascular and macrovascular complications.
For the laboratory, it must be analytically reliable.

The Analytical Responsibility of the Laboratory

As obesity prevalence rises, so does HbA1c testing volume. Screening initiatives, prediabetes monitoring, and chronic disease management programs increasingly depend on laboratory throughput and reliability.

However, HbA1c measurement is not analytically trivial.

Key Analytical Challenges

Medical scientists and biochemists are acutely aware that HbA1c results may be affected by (9):

• Hemoglobin variants (HbS, HbC, HbE, HbD)
• Elevated HbF
• Carbamylated hemoglobin in renal disease
• Altered red blood cell lifespan
• Anemia

As Ireland becomes increasingly diverse – particularly through immigration from regions with higher prevalence of hemoglobinopathies – HbA1c method selection plays a critical role in ensuring diagnostic accuracy.
A falsely elevated or falsely low HbA1c result is not merely a laboratory discrepancy. It can lead to:

• Misclassification of diabetes status
• Inappropriate treatment escalation
• Delayed intervention
• Psychological burden for patients

In obesity-driven diabetes, where early detection is crucial, analytical confidence is not optional.

Methodology Matters

Multiple analytical principles are used for HbA1c measurement:

• Capillary electrophoresis
• Ion-exchange HPLC
• Immunoassay
• Enzymatic assays

Each offers advantages, but not all provide equal capability in detecting hemoglobin variants or visualising separation patterns.
For laboratories seeking both precision and fraction resolution, capillary electrophoresis offers a powerful approach.

Capillary Electrophoresis and Analytical Confidence

Sebia CAPILLARYS 3 OCTA and TERA utilises capillary electrophoresis to separate hemoglobin fractions with high analytical resolution (10).
For hospital laboratories, key advantages include:

• Clear separation of HbA1c from other fractions
• Simultaneous detection of common hemoglobin variants
• IFCC traceability
• High throughput suitable for large clinical volumes (CAPILLARYS 3 TERA MC3 has a throughput of 176 tests/hour)
• Reproducibility aligned with tight quality specifications

The ability to visualise hemoglobin fraction patterns enhances interpretative confidence. Rather than relying solely on a reported percentage, laboratory professionals can assess separation integrity and detect potential interferences.

The Human Impact of Analytical Accuracy

It is easy to view HbA1c as a percentage, a QC metric, or a calibration curve.
But each decimal place can alter a patient’s trajectory.
For the patient with obesity on the edge of diagnosis, the difference between 47 mmol/mol and 49 mmol/mol is not abstract. It may determine whether lifestyle modification is advised or pharmacotherapy is initiated.
For the patient already diagnosed, consistent and accurate monitoring determines whether complications are prevented or allowed to progress.
On World Obesity Day, conversations often focus on prevention, lifestyle change, and policy. These are essential. But within hospital laboratories, the contribution is equally critical:
Turning metabolic risk into measurable, reliable data.

References

1. Department of Health. Healthy Ireland Survey 2024 (Government of Ireland, Dublin, 2024). Available at: https://www.gov.ie/en/healthy-ireland/publications/healthy-ireland-survey-2024/#weight-management-diet-and-nutrition (accessed 27 February 2026).
2. Hauner, H. Obesity and diabetes. In Textbook of Diabetes (eds Holt, R. I. G., Cockram, C. S., Flyvbjerg, A. et al.) 215–228 (Wiley-Blackwell, Oxford, 2010)
3. Diabetes basics (Centers for Disease Control and Prevention, 2026). Available at: https://www.cdc.gov/diabetes/about/index.html#:~:text=Type 2 diabetes accounts for,diabetes has more than doubled (accessed 27 February 2026).
4. Björntorp, P. Portal adipose tissue as a generator of risk factors for cardiovascular disease and diabetes. Arteriosclerosis 10, 493–496 (1990).
5. Cerf, M. E. Beta cell dysfunction and insulin resistance. Front. Endocrinol. 4, 37 (2013).
6. Shapiro, R., McManus, M. J., Zalut, C. & Bunn, H. F. Sites of nonenzymatic glycosylation of human hemoglobin A. J. Biol. Chem. 255, 3120–3127 (1980).
7. Higgins, P. J., Garlick, R. L. & Bunn, H. F. Glycosylated hemoglobin in human and animal red cells. Role of glucose permeability. Diabetes 31, 743–748 (1982).
8. Hussain, N. Implications of using HbA1c as a diagnostic marker for diabetes. Diabetol. Int. 7, 18–24 (2015).
9. Gallagher, E. J., Bloomgarden, Z. T. & Le Roith, D. Review of hemoglobin A1c in the management of diabetes. J. Diabetes 1, 9–17 (2009).
10. Sebia. HbA1c (Sebia, 2021). Available at: https://www.sebia.com/en-uk/tests/hba1c/ (accessed 27 February 2026).

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