Want to live longer? Research reveals the top cardiac risk factor (and it’s not smoking)
One useful takeaway here is that fitness is not just a lifestyle metric; it is also a proxy for how well the body tolerates everyday stress. That makes it clinically relevant, but it is still an association. Lower cardiorespiratory fitness may reflect deconditioning, chronic illness, age, disability, or long-standing habits, so it should not be read as the single direct cause of future risk.
The value of METs is that they translate exercise capacity into something observable. For readers, that can make progress easier to track than abstract advice like “be active.” Yet the ladder is not perfectly precise across ages, body sizes, and health conditions. A brisk walk for one person may be a meaningful workload; for another it may be too easy to change risk in the same way.
There is also a difference between improving fitness and simply doing more hard exercise. In general, gradual gains that can be sustained matter more than occasional bursts. The practical question is whether a person can safely and consistently move from one effort level to the next, because adherence and recovery influence whether the benefit lasts.
For prevention, the most actionable point is not to obsess over a single threshold. A better approach is to treat fitness as a trainable health marker alongside blood pressure, lipids, sleep, and weight-related factors. The evidence supports movement as protective, but the exact amount of benefit depends on baseline risk, medical history, and what a person can realistically maintain.
Want to predict how long you’ll live? Knowing is impossible, but there are simple research-backed tests—tests you can do for free, at home—that provide indications.
For example:
Performing relatively poorly on any of those tests correlates to a significantly greater risk of premature death—information that is interesting, but only helpful if used to make positive changes.
The key to living a longer, healthier life is to work to improve your level of health and fitness, regardless of where it currently stands. Improvement definitely correlates to greater longevity; a study published in the Journal of the American College of Cardiology (h/t to Arnold Schwarzenegger’s newsletter) determined poor fitness was linked to a greater risk of premature death than any other single cardiac risk factor.
As the researchers write, “Notably, at least a 50 percent reduction in risk can be achieved by most individuals with moderate [cardiac risk factors] for their respective age categories.”
Sounds good, but how? The key is to think about metabolic task equivalents, or METs. A MET is a measure of the ratio of the rate at which a person expends energy because of an activity. Here’s a simple breakdown:
- 1 MET: sitting at rest
- 3 to 4 METs: walking briskly, on flat ground
- 5 to 6 METs: walking briskly uphill, or lightly jogging
- 8 METs: jogging at a reasonable pace (think hard to maintain a conversation)
- 10 METs: running a 10-minute mile
- 12-plus METs: sustained, competitive-level running (for the average person, think 8-minute or below miles, a target I can no longer hit)
And here’s the thing: A study published in the Journal of the American Medical Association found that every step up the MET ladder drops your risk of death by any cause by 13 percent, and your risk of heart attack by 15 percent. Go from sedentary to being able to take a brisk walk? Your risk of death drops by 13 percent. Go from sedentary to being able to lightly jog? Now your risk of death has dropped by 26 percent.
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