How Old Are You Really? Understanding Biological vs. Chronological Age

Have you ever met someone who looks or moves like they’re years younger (or older) than their actual age? We’ve all seen it—someone in their 60s who seems full of energy and vitality, and someone much younger who struggles with fatigue or joint pain. That’s because our bodies don’t all age at the same rate.

While your chronological age is simply the number of years you’ve been alive, your biological age reflects how well your body is functioning at a cellular level. Some scientists describe it as the “true” measure of aging, as it takes into account how your organs, tissues, and systems are holding up over time. The good news? Unlike chronological age, biological age isn’t set in stone—you can influence it through lifestyle choices.

I recently listened to Dr. Valter Longo—someone I’ve followed for several years—on the ZOE Science & Nutrition podcast discussing this very subject. His research highlights how biological age is a far better predictor of health and longevity than the number on your birth certificate. Two people born on the same day can have biological ages that differ by as much as 20-25 years, depending on factors like diet, exercise, sleep, and stress management. A 50-year-old with a healthy lifestyle might have the biological age of a 40-year-old, while another 50-year-old with poor health habits could have the biological age of someone much older.

What’s even more fascinating is that research suggests biological age is a better predictor of long-term health and longevity than chronological age. In other words, how well you’re aging inside matters more than the number on your birth certificate.

Can You Influence Your Biological Age?

Yes! Studies suggest that certain lifestyle habits may slow, or even improve, biological aging, though the science in some areas is still evolving. Here’s what research currently suggests can make a difference:

✔ Fasting & Cellular Repair – Some studies indicate that periods of fasting (including time-restricted eating and fasting-mimicking diets) may trigger autophagy, a process where cells remove damaged components and regenerate. However, the research is still developing, and fasting is not suitable for everyone. More long-term studies are needed to fully understand its effects.

✔ Nutrition & Gut Health – A diet rich in whole, unprocessed foods supports a healthier microbiome, which helps regulate inflammation—a key driver of aging. Ultra-processed foods, on the other hand, can speed up biological aging.

✔ Exercise & Muscle Strength – Regular movement, especially strength training and cardiovascular exercise, maintains muscle mass, boosts metabolism, and improves cellular resilience—all critical for slowing aging. A study even found that those who exercise regularly have a biological age up to 9 years younger than their sedentary counterparts.

✔ Sleep & Stress Management – Poor sleep and chronic stress accelerate aging at the cellular level. Prioritising 7-9 hours of quality sleep and managing stress through mindfulness, movement, or relaxation techniques can help keep your biological age in check.

How Do You Measure Biological Age?

There’s no single “gold standard” test, but methods like epigenetic analysis, blood biomarkers, telomere length measurement, and metabolic assessments offer insights. Some companies even provide at-home biological age tests, though accuracy varies.

The Bottom Line

While we can’t stop chronological aging, we can take control of how well we age. By making the right lifestyle choices, we can improve not just our lifespan (how long we live) but our healthspan (how long we stay active, strong, and independent).

Disclaimer: This email is for informational purposes only and does not constitute medical advice. The research on aging and fasting is still evolving, and any significant dietary or lifestyle changes should be discussed with a qualified healthcare professional.