How Can We Define Health?

Good Health. Easy to want. Hard to define.

Everyone wishes for good health, but most have difficulty defining what good health means to them.

Dictionary definitions of health such as:

“the state of being free from illness or injury.”

don’t really capture what it is that most people are after.

When someone tells me they ‘want to be healthy, I often have no idea what it is they actually mean. I suspect they don’t, either.

So let’s get specific.

In the words of Zig Ziglar,

“You can’t hit a target you cannot see, and you cannot see a target you do not have.”

We must be precise about defining ‘health’ and what targets we will use to help guide us.

My definition of health is the optimisation of 3 separate components:

Life Span - How long you live.

Health Span - The quality of your movement and cognition.

Soul Span - The degree of meaning, value and fulfilment of your life.

Ideal health, then, would be a long life with minimal impact on your ability to do what you want to do and lived in a way that is aligned with what you believe has been the most meaningful way to spend your life.

All lives are finite, and for 90% of us, it will be ended by a chronic disease that will likely impact how we move or think in our final years.

Life Span is a binary outcome.

You are either dead or alive.

But there will come a time when you will go from alive to dead.

Health Span is a continuous variable.

You will likely have a decline in your physical and cognitive function throughout your later years, and the goal here is to delay that decline as much as possible.

Soul Span is also a continuous variable. It does not inevitably start high and then decline like ‘Health Span’. Its pattern is highly variable and is heavily dependent on your philosophy of life.

Your life will end.

Your health will decline.

But your sense of meaning and purpose in the world is always up for grabs.

Optimising your life and health span is known as ‘squaring the curve’. You aim to extend your life span and maintain your health span as much as possible for as long as possible.

This is also known as morbidity compression. The morbidity typically incurred at the end of your life as a consequence of chronic disease is ‘compressed’ into a much shorter window.

Squaring The Curve - Morbidity Compression

Life Span

“You cannot die from a condition you do not have.”

One of the key takeaways from the research on healthy centenarians is that they die from the same conditions as everyone else, but they get those conditions about 20 to 25 years later than everyone else1. This may sound like a very mundane point but embedded in this piece of information is a significant lifespan pearl.

If you want to live longer, you have to focus on delaying the onset of the medical conditions that are likely to kill you rather than relying on aggressively treating them when they do appear.

Remember that 90% of adults will die from a noncommunicable chronic medical illness2. Think cardiovascular disease, cancer or dementia.

This is a game of odds.

It is about understanding what tilts the probabilities in your favour and doing everything to advantage yourself.

This is about doing everything possible to avoid developing the risk factors for the conditions we mentioned. If you have developed one of these risk factors, be as aggressive as possible about minimising its impact.

Health Span

The key determinants of your health span will be the quality of your movement and cognition.

Your quality of movement will be a function of how much you have invested in maintaining muscle mass, muscle strength, flexibility, stability and aerobic capacity by way of your V02 max & lactate thresholds etc.

These metrics of physical ability decrease over time, and if your starting point in midlife is below average, you cannot expect to be above average in your final years of life.

Think of this as your movement pension. You need to be making regular contributions to weather that big drawdown that life imposes at the end.

Your cognition is a function of delaying or preventing dementia. Although there are genetic causes of dementia, a significant amount of the variability relates to a handful of lifestyle factors ranging from physical activity to your degree of social interactions3.

Similar to life span, optimising health span also comes down to probabilities.

Soul Span

Living a life of meaning and purpose is a question that philosophers have been asking for thousands of years.

A key distinction here is that this is not the pursuit of happiness.

It is something much deeper.

Happiness is fleeting.

You get a new car. It smells great. You feel happy when you drive it for the first time. But that feeling soon fades, and soon that new car is just ‘your car’. This is what is known as the ‘hedonic treadmill’. An idea that people trend back to their baseline level of happiness regardless of what short-lived material gains they make in life.

A life of meaning and purpose captures much more than temporary pleasures. Some have suffered greatly, died far younger than they should have, and have lived immensely meaningful lives.

A life of meaning is about living a life that aligns most closely with the most honest appraisal of ‘who you are’. This is why Socrates proclaimed that we must:

Know thyself”.

This step is the foundation stone of Soul Span.

The challenge is that this foundation stone evolves over time, and in the modern world if you do not work hard to define this parameter for yourself, the world will be happy to define it for you.

And you will not be the better for it.

As Carl Jung notes:

"The world will ask you who you are, and if you do not know, the world will tell you."



Ultimately the goal should be to optimise all three components of health.

Optimal Life Span, Health Span and Soul Span.

Having good health is a worthy goal.

But we must be clear about what that goal is.

Without precision, we will likely wander aimlessly, never defining or achieving the health goals we had hoped for. And even if we did, we would probably not recognise them should we achieve them.

The next time you think about your health, evaluate that question through the lens of:

Life Span

Health Span &

Soul Span.

It’s not the only way to do it.

But it’s an excellent place to start.


Health span approximates life span among many supercentenarians: compression of morbidity at the approximate limit of life span. J Gerontol A Biol Sci Med Sci. 2012 Apr;67(4):395-405.



Association of Combined Healthy Lifestyle Factors With Incident Dementia in Patients With Type 2 Diabetes. Neurology Sep 2022, 10.1212/WNL.0000000000201231;

When You Are Ready Here Is How I Can Help You.

The Heart Health Formula Is Everything I Have Learned About Heart Disease Prevention Over The Last 20 Years About.

This is the formula for preventing heart disease and living longer.

Click on the button below to learn more.

Tell Me More

The Real Secret Of Why Blue Zones Have Exceptional Longevity

How to Define Exercise Zones for Optimal Workout Efficiency. The Es...

Five Simple Tests You Can Do At Home To See How Long You Will Live.


Prevent Heart Disease. Live Longer. 

Join 20K+ Others On My Free Weekly Email For Actionable Insights.