The 8 Numbers Every Adult Should Know by 40

Most people monitor familiar health metrics such as weight, cholesterol, and blood pressure. Yet these measures offer only a partial view of long-term health.

The data that most reliably predicts outcomes such as cardiovascular disease, metabolic dysfunction, and overall longevity is often hidden, overlooked, or never measured.

Over the past five years building Fitnescity Health and partnering with nearly a thousand hospitals, imaging centers, and academic institutions, I’ve had a front-row seat to how dramatically the right data can change a person’s understanding of their health. Certain metrics surface early signals that routine exams miss. Others reveal risks years before symptoms appear.

This article highlights eight numbers that, taken together, provide one of the clearest and most actionable snapshots of long-term health. They are grounded in decades of research, widely used in clinical practice, and — importantly — accessible to anyone willing to measure them.

1. VO2 Max: Your Body’s Engine Power

If I had to pick a single number that predicts longevity better than almost anything else, it’s VO2 Max.

VO2 Max measures how much oxygen your body can use during exercise. Higher levels are strongly associated with lower rates of cardiovascular disease, metabolic disease, and even all-cause mortality.

The best part? It’s highly modifiable.

Unlike many health metrics, you can improve VO2 Max within weeks through structured training.

2. Coronary Calcium Score: A Look Inside Your Arteries

The Calcium Score is one of the most powerful predictors of future heart disease ever discovered.

It quantifies calcified plaque in your coronary arteries—the buildup that leads to heart attacks. The test is quick, painless, and incredibly actionable: a score of zero is reassuring, while a higher score guides conversations with your clinician on how to reduce risk.

This is the one number on this list you can’t change — but knowing it can change your future.

3. DEXA Body Composition: Beyond Weight, Toward What Matters

Your weight doesn’t tell you whether you’re healthy. Body composition does.

A DEXA scan breaks down your body into:

• Lean mass (muscle)
• Fat mass
• Visceral fat — the dangerous fat around your organs

High visceral fat is strongly tied to metabolic disease and early cardiovascular risk. Maintaining muscle mass is one of the best predictors of healthy aging — especially after 40.

4. Resting Metabolic Rate (RMR): Your Metabolism’s Baseline

RMR tells you how many calories your body burns at rest. It’s the foundation of energy balance and deeply linked to metabolic health.

A low or unexpectedly slow RMR may signal hormonal changes, loss of muscle mass, or early metabolic dysfunction. A healthy, higher RMR is often a sign of good metabolic flexibility and lean mass.

5. Hemoglobin A1C: Your Long-Term Glucose Picture

A1C reflects your average blood sugar over the past three months.

Even mildly elevated levels — long before diabetes — are associated with increased cardiovascular risk, cognitive decline, and metabolic dysfunction.

This number often changes silently, which makes it essential to track.

6. ApoB: The Most Powerful Lipid Number Most People Don’t Know

If you’ve only been checking LDL cholesterol, you’re missing the full picture.

ApoB measures the actual number of atherogenic particles that drive plaque formation. It’s a far stronger predictor of cardiovascular risk than LDL alone — and it’s becoming the new standard among cardiologists and longevity physicians.

7. hsCRP: The Inflammation Signal

Chronic inflammation increases the risk of heart disease, cancer, and metabolic disorders.

hsCRP (high-sensitivity C-reactive protein) is a simple marker that reflects low-grade systemic inflammation. It’s sensitive, predictive, and modifiable through lifestyle, stress management, and clinical interventions.

8. Blood Pressure: The Silent Risk Multiplier

High blood pressure is one of the most common — and most overlooked — risk factors for heart disease and stroke.

It often rises gradually, with no symptoms, and amplifies the danger of other risk factors like high ApoB or elevated A1C.

Blood pressure is not just a number; it’s a lens into the health of your vascular system.

Why These 8 Numbers?

Three reasons:

1. They predict the health outcomes that matter most.

Cardiovascular disease, metabolic disease, and chronic inflammation underpin most long-term health risks.

2. They’re modifiable — you can act on them.

Except for the Calcium Score, each number can be improved with lifestyle, training, or medical guidance.

3. Together, they give a full-body picture.

Performance, structure, metabolism, inflammation, vascular health. Eight numbers — no redundancy, no noise.

The Future of Preventive Health Is Data You Can Use

At Fitnescity Health, this philosophy guides everything we do. Whether it’s VO2 Max, DEXA body composition, metabolic tests, or the Cardiac Calcium Score, our goal is simple:

Help people know their numbers and take control of their health before problems arise.

Prevention isn’t guesswork. It’s measurement, understanding, and action.

These eight numbers are a powerful place to start.

— Laila Zemrani Co-Founder & CEO, Fitnescity Health

About Own Your Health

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Note: Nothing in this article constitutes medical advice, diagnosis, or treatment. Always seek the advice of your doctor or a qualified medical professional if you have any questions about your health, well-being, or Fitnescity Health test. results.