Daniel López

“A person who smokes has a 40 percent greater risk of all-cause mortality (that is, risk of dying at any moment) than someone who does not smoke, representing a hazard ratio or (HR) of 1.40. This study found that someone of below-average VO2 max for their age and sex (that is, between the 25th and 50th percentiles) is at double the risk of all-cause mortality compared to someone in the top quartile (75th to 97.6th percentiles). Thus, poor cardiorespiratory fitness carries a greater relative risk of death than smoking. That’s only the beginning. Someone in the bottom quartile of VO2 max for their age group (i.e., the least fit 25 percent) is nearly four times likelier to die than someone in the top quartile—and five times likelier to die than a person with elite-level (top 2.3 percent) VO2 max. That’s stunning. These benefits are not limited to the very fittest people either; even just climbing from the bottom 25 percent into the 25th to 50th percentile (e.g., least fit to below average) means you have cut your risk of death nearly in half, according to this study.”
― Peter Attia, Outlive: The Science and Art of Longevity