The Maximum Human Life Span and Conjecture on Step Counts to Get There (15,000 Steps a Day)

“For the study, Timothy Pyrkov, a researcher at a Singapore-based company called Gero, and his colleagues looked at this “pace of aging” in three large cohorts in the U.S., the U.K. and Russia. To evaluate deviations from stable health, they assessed changes in blood cell counts and the daily number of steps taken and analyzed them by age groups.

For both blood cell and step counts, the pattern was the same: as age increased, some factor beyond disease drove a predictable and incremental decline in the body’s ability to return blood cells or gait to a stable level after a disruption. When Pyrkov and his colleagues in Moscow and Buffalo, N.Y., used this predictable pace of decline to determine when resilience would disappear entirely, leading to death, they found a range of 120 to 150 years…

The researchers also found that with age, the body’s response to insults could increasingly range far from a stable normal, requiring more time for recovery. Whitson says that this result makes sense: A healthy young person can produce a rapid physiological response to adjust to fluctuations and restore a personal norm. But in an older person, she says, “everything is just a little bit dampened, a little slower to respond, and you can get overshoots,” such as when an illness brings on big swings in blood pressure.”

-Emily Willingham, “The Maximum Human Life Span Is 150 Years, New Research Estimates
A study counts blood cells and footsteps to predict a hard limit to our longevity
.” Scientific American. May 25, 2021.

Open Questions: How many steps a day are required for optimum fitness and health? Is there also a strength measurement that can be used to add an additional dimension?

The Nature research article is available online. I think the interesting thing about this study is it is another example where step counts are used as a proxy for health. There are recent studies in JAMA, Journal of Sport and Health Science, and others that suggest that increasing step counts lowers overall morbidity and mortality in older adults.

As an N of 1 thought experiment, I checked my daily step count over the last year. I average just over 10,000 steps a day. There are studies that classify step counts in the following way:

  • sedentary category (<5000 steps/day)
  • low active (5000-7499 steps/day),
  • somewhat active (7500-9999 steps/day)
  • active (≥10,000 steps/day)

The same study also makes the following observation: “We also observed that each 1000 steps/day increase in [physical activity] level over the 6-month follow-up was associated with a 0.26-kg (95% CI −0.29 to −0.23) [or just over 0.5 pounds] decrease in weight.”

The math is pretty easy. Let’s suppose 1,000 steps is about half a mile or a kilometer. That’s about ~60-75 calories, depending on intensity, walking or running. Let’s say 6 months is 182 days. So, 60 calories * 182 days = ~11,000 calories. That’s about 3 pounds or a bit over a kilo. Factor in additional urge to eat, and it sounds about right.

So, as a rule of thumb: Increasing step counts by 1,000 will generally reduce your weight by 1 pound a year, as well as your overall risk of morbidity and mortality. There’s probably some point of negative returns. I’ve seen some reports talking about hunter-gatherer groups walking on average around 7 or 8 miles a day, which would roughly be around 14,000 to 16,000 steps / day, which is probably a good benchmark comparison with humanity over an evolutionary time frame rather than comparing our activity with other people in our historical moment. Which I suppose suggests that I, and practically everyone, have some work to do to get our physical activity to an optimum level.