- Five modifiable numbers predict how well you age: cardiorespiratory fitness, ApoB, fasting insulin, blood pressure, and muscle strength.
- Each is trackable, each is changeable, and together they beat almost any single test for predicting long-term health.
- Most require only inexpensive, widely available measurement — strategy and consistency matter more than exotic panels.
- These are early-warning and early-action metrics: they move years before disease, when intervention is easiest.
If you want to know how the next decade of your health is likely to go, you do not need a crystal ball or a $5,000 panel. You need five numbers. Each one is modifiable, each is measurable, and together they predict how well you will age better than almost any single test in medicine. Track these, act on the weakest, and you are doing the most important work in preventive health.
1. Cardiorespiratory fitness
If there is a king metric, this is it. Your fitness — how well your heart, lungs, and muscles use oxygen — is one of the strongest predictors of survival ever measured. A large study of adults undergoing treadmill testing found that higher fitness was associated with dramatically lower long-term mortality, with essentially no upper limit to the benefit. Crucially, fitness is trainable at any age. It is both a warning light and a lever.
2. ApoB
When it comes to heart disease, the number to know is not just your standard cholesterol — it is ApoB, a measure of the actual atherogenic particles that drive plaque. Each of those particles carries one ApoB protein, so ApoB counts the "delivery trucks" of cholesterol into your artery walls. Research increasingly shows ApoB predicts cardiovascular risk more accurately than LDL cholesterol alone. Ask for it; many people never have.
3. Fasting insulin
Here is the most under-ordered high-value test in medicine. Insulin rises to keep blood sugar normal for years before glucose itself climbs — so a normal glucose can hide early insulin resistance, the quiet root of diabetes, heart disease, and more. Fasting insulin (and the HOMA-IR calculated from it) catches that drift while it is still highly reversible.
4. Blood pressure
The most common reversible driver of stroke and heart disease, and one of the easiest to track — a home cuff and a weekly habit. Blood pressure tends to creep up slowly and silently, which is exactly why watching the trend matters. Generally, under 120/80 is the goal, but interpret yours with your clinician.
5. Muscle strength
Strength — often measured simply as grip — predicts future disability, independence, and all-cause mortality. In a 17-country study, each 5 kg drop in grip strength was linked to a 16% higher risk of death from any cause. Grip is a cheap readout of whole-body muscle and neurological health, and, like fitness, it is trainable. What you build now is the independence you keep later.
How to use them
The power of these five is not in obsessively optimizing all at once — it is in finding your weakest link and improving it. Measure your baseline, see which number is lagging, and direct your effort there. Low fitness? Build an aerobic base. High fasting insulin? Muscle, movement, and nutrition. Creeping blood pressure? Sleep, salt, stress, and exercise. Then re-measure. These are not numbers to admire; they are numbers to move — and moving them, decade by decade, is how you write a healthier future while you still have the pen.
In practice: why this matters
Healthcare largely waits to measure risk until disease has arrived — a blood pressure at the stroke, a glucose at the diabetes diagnosis. Building everyday care around a few forward-looking, modifiable numbers would shift medicine from reaction to prevention. These five metrics are cheap, actionable, and predictive; making them routine could prevent an enormous amount of late-life disease at a population scale.
Frequently asked questions
If I can only track one, which matters most?
Cardiorespiratory fitness. It is one of the strongest predictors of survival known — a review found each higher increment of fitness meaningfully lowers mortality — and it is trainable at any age. In practice, though, these five work together, and the weakest one is usually where your biggest gains are.
Do I need a fancy clinic to measure these?
No. Blood pressure needs a home cuff; fasting insulin and ApoB are standard blood tests; strength can be tracked with grip or your own lifts; and fitness can be estimated from a repeatable exercise test or even how you handle a brisk hill. Strategy and consistency beat expensive panels.
References
- Mandsager K, Harb S, et al. Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing. JAMA Network Open. 2018;1(6):e183605. doi:10.1001/jamanetworkopen.2018.3605
- Leong DP, Teo KK, et al. Prognostic value of grip strength: findings from the PURE study. The Lancet. 2015;386(9990):266–273. doi:10.1016/S0140-6736(14)62000-6
- Glavinovic T, Thanassoulis G, et al. Physiological Bases for the Superiority of Apolipoprotein B Over LDL-C and Non-HDL-C as a Marker of Cardiovascular Risk. Journal of the American Heart Association. 2022;11(20):e025858. doi:10.1161/JAHA.122.025858
Peer-reviewed sources located via PubMed and cited for education. Citations reflect published research at time of writing.
Dr. Andrew Simon, ND, BCB
Licensed naturopathic physician and board-certified biofeedback practitioner in Seattle. Clinic Director of Rebel Med NW, adjunct clinical faculty at Bastyr University, six-time Seattle Met Top Doctor, and the naturopathic advisor to Washington State on Long COVID. Read full bio →
This article is for educational purposes and is not a substitute for individualized medical care. Talk with a qualified clinician about your specific situation.