“The story is far more complicated, and more interesting, than a single number suggests.”
When people ask about my health, I sometimes mention my “metabolic age”. It’s a term that’s become popular in gyms, clinics and wellness apps, promising to reveal how old your body really is on the inside. But as someone who works in health policy, lives with obesity and thyroid disease, and happens to be a Black, middle-aged woman, I’ve learned that the story is far more complicated, and more interesting, than a single number suggests.
The Problem with One-Size-Fits-All Metrics
“Health isn’t one-size-fits-all – yet our most common metrics pretend it is.”
Most health systems and clinicians still rely on traditional metrics: body mass index (BMI), basal metabolic rate (BMR), and weight. These are easy to measure and compare, but they don’t capture the full picture. For example, BMI doesn’t distinguish between muscle and fat, and BMR calculations often ignore differences in ethnicity, body composition, and health status.
In my own case, a standard BMR-based calculation puts my metabolic age at 45. That’s not bad for someone who’s 53. But when I factor in my muscle mass, metabolic health, inflammation markers, and my Afro-Guyanese heritage, known to be associated with higher lean mass and bone density, my “functional metabolic age” drops to 36–37.
“When I factor in my muscle mass, metabolic health, inflammation markers, and my Afro-Guyanese heritage… my ‘functional metabolic age’ drops to 36–37.”
Why Does This Matter?
Research shows that up to 30% of people with obesity are “metabolically healthy” by traditional markers, yet still at risk for functional decline Muscle mass, which declines by 3–8% per decade after age 30, is a key predictor of healthy ageing and independence. And for people of African descent, standard charts can underestimate health potential, leading to misclassification and missed opportunities for prevention.
“Standard charts can underestimate health potential.”
Globally, obesity-related healthcare costs account for up to 7% of total health expenditure. As the World Health Organization and other bodies call for more person-centred, value-based care, it’s time to ask whether our metrics are fit for purpose.
Towards a More Meaningful Measure
“It’s not just about how many calories you burn at rest, but how well your body actually works.”
Functional metabolic age is a composite measure that integrates muscle mass, metabolic health, inflammation, and ethnicity. It’s not just about how many calories you burn at rest, but how well your body actually works. This approach is gaining traction in research and policy circles, with initiatives like the IMI-SOPHIA and the Mayo Clinic advocating for phenotype-guided, functional targets in obesity care.
Recent updates to the EASO Obesity Algorithm reflect this shift. The EASO algorithm now recommends a comprehensive, phenotype-driven assessment, including body composition, metabolic health, and functional status, before selecting interventions. Crucially, EASO acknowledges that ethnicity and individual variation must be considered when interpreting BMI and metabolic risk, echoing the need for more nuanced, equitable approaches in both clinical and policy settings.
“It’s a way to acknowledge the strengths and risks that come with my unique biology and background.”
For me, sharing my functional metabolic age is about accuracy and equity. It’s a way to acknowledge the strengths and risks that come with my unique biology and background, and to advocate for health systems that recognise and respond to diversity.
What’s Next?
“Obesity is about biology, phenotypes, function, and identity.”
Obesity is about biology, phenotypes, function, and identity. As more health systems move towards value-based and treatment-to-target models, I hope we’ll see a shift towards metrics that reflect what really matters: quality of life, independence, and healthspan.
“So next time you hear someone talk about their metabolic age, ask them: which one?”
Disclosure: Jacqueline Bowman is a health policy expert and advocate with lived experience of obesity and thyroid disease. She is Founder at Third-i bv, a mission-driven small business, and her work focuses on equity, patient-centred care, and health system transformation.