Biological Age: Is Your Body Older or Younger Than You?

Chronological vs biological age

Chronological age is straightforward. It is the number of years since you were born. It moves forward at the same rate for everyone, and there is nothing you can do to change it.

Biological age is different. It reflects how well your body actually functions compared to others of the same chronological age. It is shaped by genetics, lifestyle, environment, and the accumulated effects of daily habits over years and decades.

Two 40 year olds can have very different biological ages. One who exercises regularly, sleeps well, manages stress, and eats a balanced diet may have the cardiovascular fitness and cellular markers of a 32 year old. Another who is sedentary, chronically stressed, and sleep deprived may function more like a 50 year old.

The key difference is that biological age is modifiable. While you cannot change when you were born, you can influence the rate at which your body ages.

Research published in Aging Cell has shown that interventions targeting lifestyle factors can meaningfully shift biological age markers in as little as eight weeks, demonstrating that the body responds quickly to positive changes even after years of suboptimal habits.

Key biomarkers of biological age

Researchers use a variety of biomarkers to estimate biological age. These fall into two broad categories:

Traditional lab based markers

• Telomere length: Telomeres are protective caps on the ends of chromosomes that shorten with age. Shorter telomeres are associated with faster biological aging.
• DNA methylation: Epigenetic clocks like Horvath's clock measure chemical modifications to DNA that correlate with aging. These are currently the most accurate lab based measures of biological age.
• Blood markers: Fasting glucose, cholesterol levels, inflammatory markers like C reactive protein, and insulin sensitivity all provide data points about how your body is aging.

Wearable accessible markers

• VO2 Max: The gold standard measure of cardiorespiratory fitness. Strongly correlated with all cause mortality and biological age.
• Heart rate variability (HRV): Reflects autonomic nervous system health and declines predictably with age.
• Resting heart rate: A lower resting heart rate generally indicates better cardiovascular fitness.
• Sleep efficiency: The percentage of time in bed actually spent sleeping. Declines with biological aging.
• Walking speed: Research consistently links gait speed to longevity and overall functional health.
• Grip strength: A surrogate marker for overall muscular health and strongly predictive of aging outcomes.
• Body composition: The ratio of lean mass to fat mass shifts with aging and reflects metabolic health.

No single marker tells the whole story. The most robust biological age estimates combine multiple indicators to create a composite picture. This multi marker approach is more resilient to noise from any individual metric having an off day.

Lab tests vs wearable estimates

Lab based biological age tests have become increasingly sophisticated. GrimAge, PhenoAge, and DunedinPACE are epigenetic clocks that analyze DNA methylation patterns from blood samples. They offer high precision but come with trade offs: they are expensive, require a blood draw, and only provide a snapshot at a single point in time.

Wearable estimates take a different approach. They use surrogate markers like VO2 Max, HRV, resting heart rate, and sleep data that correlate with biological age. These estimates are less precise than molecular testing, but they offer something lab tests cannot: daily updates that let you track the direction of change over time.

Think of it this way. A lab test tells you exactly where you are today. A wearable estimate tells you whether you are moving in the right direction.

Laso's Vitality Age uses 9 wearable accessible indicators updated daily to give you a continuous picture of how your body is aging. It does not replace clinical testing, but it fills the gap between annual checkups with actionable data.

What moves the needle

The factors that most strongly influence biological age are well established by research:

• Exercise: The single strongest factor. Both aerobic and resistance training reduce biological aging markers. VO2 Max improvement through consistent aerobic training has the largest individual impact on estimated fitness age.
• Sleep quality: Consistently poor sleep accelerates biological aging. Adequate, high quality sleep supports cellular repair and hormonal balance.
• Stress management: Chronic psychological stress increases inflammatory markers and accelerates telomere shortening.
• Nutrition: A diet rich in whole foods, vegetables, lean protein, and healthy fats supports metabolic health and reduces oxidative stress.
• Body composition: Maintaining a healthy ratio of lean mass to body fat is strongly associated with slower biological aging.
• Not smoking: Smoking accelerates nearly every marker of biological aging.
• Limiting alcohol: Even moderate alcohol consumption has been linked to faster epigenetic aging in recent large scale studies.

Of these, improving VO2 Max through regular aerobic exercise is the most actionable lever for most people. A landmark study in JAMA Network Open found that each 1 MET increase in fitness was associated with a 13% reduction in all cause mortality.

Why VO2 Max is the standout metric

Among all the wearable accessible biomarkers of biological age, VO2 Max stands out for its strength of association with longevity. VO2 Max measures the maximum amount of oxygen your body can use during intense exercise. It reflects the combined efficiency of your heart, lungs, blood vessels, and muscles.

A large meta analysis in the British Journal of Sports Medicine found that low cardiorespiratory fitness was a stronger predictor of all cause mortality than smoking, hypertension, or high cholesterol. People in the lowest fitness quintile had roughly four times the mortality risk of those in the highest quintile.

The practical implication is clear. Improving your VO2 Max through regular aerobic training is one of the single most impactful things you can do to slow biological aging. Even modest improvements, moving from "below average" to "average" for your age, carry significant mortality reduction.

VO2 Max can be estimated from wearable data during outdoor walks, runs, or cycling sessions. While these estimates are less precise than lab testing with a metabolic cart, they are accurate enough to track direction of change, which is what matters for biological age monitoring.

The good news is that VO2 Max is highly trainable at any age. Studies on adults in their 60s and 70s who began structured aerobic training showed VO2 Max improvements of 15 to 20 percent within six months. From a biological age perspective, this can translate to a functional fitness level matching someone 10 to 15 years younger.

Tracking biological age over time

A single biological age measurement, whether from a lab test or a wearable estimate, is useful but limited. The real value comes from tracking the trend over months and years. Are you aging faster or slower than the calendar?

Wearable based tracking makes this practical. Rather than getting an expensive blood test once or twice a year, you can see daily updates that reflect the cumulative impact of your habits. A month of consistent exercise and good sleep will show up in your numbers. So will a month of poor sleep and elevated stress.

This feedback loop is what makes biological age tracking actionable. It connects daily choices to measurable outcomes in a way that annual lab tests cannot.

Laso's Vitality Age provides this continuous tracking, updating daily and showing long term trends so you can see whether your lifestyle choices are moving the needle in the right direction.

Common misconceptions

There are several misunderstandings about biological age worth addressing:

• Biological age is not fixed by genetics. While genetics play a role, research on identical twins shows that lifestyle factors account for the majority of variation in biological aging after middle age. Your choices matter more than your genes.
• You cannot reverse aging to zero. When people talk about "reversing" biological age, they mean slowing the rate of aging or improving function to match a younger age group. No intervention reverses aging at the cellular level entirely.
• Supplements alone will not change your biological age. No supplement has demonstrated the same magnitude of effect as regular exercise, quality sleep, and stress management. Fundamentals come first.
• A single metric is not enough. No single biomarker, whether VO2 Max, HRV, or telomere length, captures the full picture. Biological age is best estimated from multiple indicators considered together.

How different lifestyles show up in the data

The biomarkers that make up biological age respond predictably to different lifestyle patterns. Understanding this can help you see why certain habits matter more than others.

A person who runs three to four times a week and sleeps seven to eight hours consistently will typically show an above average VO2 Max, higher HRV, lower resting heart rate, and better sleep efficiency. These markers together paint a picture of a body that is aging more slowly than average.

Someone who is mostly sedentary, sleeps irregularly, and carries chronic stress will often show the opposite pattern: lower VO2 Max, suppressed HRV, elevated resting heart rate, and poor sleep efficiency. Each metric individually might look unremarkable, but together they indicate accelerated biological aging.

The encouraging finding from longitudinal research is that these patterns are reversible. Studies on previously sedentary adults who began regular exercise programs showed measurable improvements in biological age markers within 8 to 12 weeks. The body responds quickly to positive changes.

This is why daily tracking is valuable. It makes the connection between behavior and biological outcome visible, creating a feedback loop that reinforces healthy habits.

Getting started with biological age tracking

If you want to start monitoring your biological age, here is a practical approach:

• Wear your device consistently. Biological age estimates improve with more data. Wearing your Apple Watch or other wearable through the night and during exercise gives the most complete picture.
• Establish a baseline. The first two to four weeks of data collection establish your personal baseline. Avoid making major lifestyle changes during this period so the baseline accurately reflects your starting point.
• Focus on trends, not daily numbers. Individual readings fluctuate. Look at 7 day and 30 day averages to see the real signal beneath the noise.
• Make one change at a time. If you want to see what moves your biological age, changing one variable at a time makes it clearer which habit is having an effect.

The goal is not to obsess over a number. It is to have a reliable signal that tells you whether your body is moving in the right direction over the months and years that matter.

Consider pairing wearable tracking with periodic lab work. An annual blood panel covering fasting glucose, lipid profile, inflammatory markers, and basic metabolic panel provides clinical depth that complements the continuous signal from your wearable. Together, they give both breadth and precision.

For most people, the wearable data alone is enough to guide daily decisions and track long term progress. Lab tests add clinical context at key checkpoints along the way.