If you pluck someone off the street, whether in New York or Wichita or Seattle or Sacramento, and ask them how many steps people should aim for per day in order to get enough physical activity, they’ll probably tell you 10,000. In an age in which pedometers are cheaper, more accurate, and more feature-rich than ever, this number has taken on almost mythical proportions — a lofty-sounding goal (in reality, it’s approximately five miles, and a reasonably active person can pull it off fairly easily) that separates the active-lifestyle haves from the slothful have-nots.

But is there any medical reason to embrace this number? Not really. That’s because the 10,000-steps-a-day recommendation has nothing to do with sedentary, fast-food-drenched circa-2015 America. Rather, the recommendation first popped up in a very different food and environment: 1960s Japan.

“It basically started around the Tokyo Olympics” in 1964, said Catrine Tudor-Locke, a professor who studies walking behavior at LSU’s Pennington Biomedical Center. “A company over there created a man-po-kei, a pedometer. And man stands for ‘10,000,’ po stands for ‘step,’ and kei stands for ‘meter’ or ‘gauge.’” Ten thousand, it turns out, “is a very auspicious number” in Japanese culture, said Theodore Bestor, a Harvard researcher of Japanese society and culture, in an email. “That is, it seems likely to me that the 10,000 steps goal was subsidiary to having a good-sounding name for marketing purposes.” Whatever the reason for the adoption of this particular number, “It resonated with people at the time, and they went man-po-kei-ing all over the place,” said Tudor-Locke.

The problem, which barely needs stating, is that circa-1964 Japan was markedly different from the circa-2015 U.S. “By all accounts, life in Japan in the 1960s was less calorie rich, less animal fat, and much less bound up in cars,” said Bestor. Data from the Food and Agriculture Organization of the United Nations shows that the average per-capita food supply for Japanese people in 1964 was 2,632 calories, while the average for Americans in 2011 was 3,639. That’s a difference of about 1,000 calories — or, if you’re keeping track, about 20,000 steps for an average-size person. (Jean Buzby of the USDA said in an email that food supply is a commonly used rough proxy for food consumption.)

These sorts of numbers all vary hugely, of course, depending on region, social demographics, and a variety of other factors. But the point is no one can argue that Japanese people in the 1960s lived in the same sort of nutritional environment as Americans in 2015.

More broadly, 10,000 steps is just a bit too simplistic a figure, say nutrition researchers. All the ones I spoke to agreed that there’s nothing wrong with shooting for 10,000 steps, per se, and that on paper, walking (or doing any physical activity) more is better than walking less. But Tudor-Locke said that “The one-size-fits-all [approach] doesn’t necessarily work.”

Her work focuses on the most sedentary slice of the population (a rather big slice slice in the U.S.), and there, it can be a challenge to get people to take 5,000 steps, let alone 10,000. But moving from 2,500 steps a day, say, to 5,000, is a small but important victory for people who don’t get any exercise, and can have important health ramifications. “We know that you get the biggest bang for your buck by just moving from a sedentary state up a little bit,” she said.  “Your biggest bang comes from rolling off the couch and being active.” A big European study published in January that looked at the mortality rates for people with different activities levels, in fact, found that “a markedly reduced hazard was observed between those categorized as inactive and those categorized as moderately inactive” — a 20 to 30 percent reduction.

People in these categories, who at the moment are getting almost no exercise, aren’t going to benefit from the 10,000-steps recommendation. In fact, it might deter them from exercising, said Tudor-Locke. “For people who are very inactive or chronically ill or whatever have you, that might be a huge jump for them,” she said, “and that might be intimidating for them.” If the 10,000-steps goal has this effect, “then it loses its purpose.” From a public-health perspective, she said, a more pressing, realistic goal is “to get people away from taking less than 5,000” steps a day.

In a country where people eat really, really poorly, there’s also a chance that fixating on the 10,000-step milestone will lead people to neglect other, potentially important factors like their  diet. “Focusing exclusively on how many steps you’re getting and neglecting those other aspects isn’t going to lead to an overall improvement in health, unless you’re addressing those other factors simultaneously,” said Jeff Goldsmith, a biostatistics professor at Columbia’s Mailman School of Public Health.

In other words: Yeah, 10,000 steps is great, but if you follow up those 10,000 steps by buying a 500-calorie hamburger — and, more generally, spend the rest of your day eating junk — you can still gain weight and face all sorts of unpleasant negative health outcomes. “What we know from the scientific evidence is that diet and physical activity are relatively separate domains,” said Dr. Eric Rimm of the Harvard School of Public Health. “There are people who are overweight and eat poorly and still exercise, and on the other hand, there are people who eat really well but sit on the couch.” An overly narrow focus on 10,000 doesn’t encourage an integrated approach to getting healthier.

Finally, 10,000 steps might “be too low for children,” said Jean Philippe-Walhin, an exercise researcher at the University of Bath — and kids these days, as you’re probably already aware, aren’t doing so hot on the obesity front.

So while 10,000 steps is fun and easy to remember and a catchy marketing tool in (at least) two languages, maybe it’s time, given just how unhealthy so many people are and how much they’d benefit from moving around just a little more, to embrace an incremental-improvement approach to exercise. But even if the science of nutrition and exercise is complicated, that doesn’t mean the take-home message needs to be. “Stand rather than sit, walk rather than stand, jog rather than walk, and run rather than jog,” wrote Ulf Ekelund, lead author of the European mortality study, in an email. Tudor-Locke distilled things even further: “Just move more than before,” she said. “Keep moving more than before.”

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Science of Us is a smart but playful window into the latest science on human behavior, with the goal of enlightening, entertaining, and providing useful information that can be applied to everyday life.