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Why Do People Like Running? It’s Hormonal, Study Finds

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We recently reported on a study that says serious runners marking their miles tend to think about how running kind of sucks. But how do you square that negativity with the well-known, widely reported euphoria known as runner's high? 

A new study in the journal Cell Metabolism suggests that high is the result of a decrease in the hormone leptin, which is associated with feeling sated. As your levels of leptin dwindle, they send a hunger signal to your brain, which releases dopamine to increase your stamina and keep you running in the pursuit of food. 

In the study, mice were genetically altered to interfere with their brains’ leptin signaling pathways, disrupting the release of dopamine in response to leptin. These mice ran twice as many miles on their wheels as normal mice. The decrease in leptin signaling seemed to increase the dopamine-related reward associated with running, inducing positive feelings about the task at hand—an advantage if your body thinks you're hungry and needs nutrients.

"Based on these findings, we think that a fall in leptin levels increases motivation for physical activity as a means to enhance exploration and the pursuit of food," study co-author Stephanie Fulton, a researcher at the University of Montreal, says in a press statement. “Our study also suggests that people with lower fat-adjusted leptin levels, such as high-performance marathon runners, could potentially be more susceptible to the rewarding effects of running and thus possibly more inclined to exercise,” she explains. 

Leptin probably isn’t the only hormone involved in runner’s high, but it does seem to play a vital role. Previous research has also connected lower leptin levels with the desire to move, finding associations with low leptin levels and exercise addiction as well as hyperactivity in anorexic patients

[h/t: Washington Post]

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Where in the U.S. People Aren't Getting Enough Exercise, Mapped
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The U.S. is a notoriously sedentary country. A huge portion of the population doesn't meet the government's recommendations for physical activity, and that can have some serious ramifications for public health. But not everyone is equally sedentary. Physical activity rates can vary significantly from state to state, as a CDC report spotted by Thrillist illustrates.

The U.S. government currently recommends that adults squeeze in 150 minutes of moderate physical activity each week, or 75 minutes of vigorous activity, plus two days a week of "muscle strengthening activities" like weight lifting or calisthenics. Across the board, the number of Americans between the ages of 18 and 64 who actually meet that recommendation hovers at around 23 percent, but some states are much more physically active than others. (Men were also more likely to meet the recommendation than women, and working people were more likely than non-working people to get the recommended amounts of exercise.) The map below draws on data from the 2010 to 2015 National Health Interview Surveys, part of which included questions about exercise habits.

A color-coded map of activity rates in the U.S. with active states in blue and inactive states in red
Age-adjusted percentages of adults aged 18–64 who met federal guidelines for physical activity from 2010-2015
National Center of Health Statistics

Some of the states with the highest rates of exercise are ones we already associate with health and outdoor activity. California, for instance, scores relatively high, with 24 percent of adults meeting the guidelines. Colorado has the highest percentage, at 32.5 percent. Meanwhile, the South, a region already associated with high rates of obesity and poor public health, has some of the lowest activity rates, including 13.5 percent in Mississippi.

It's not just a matter of region, though. Much of the Midwest, including Kansas, Nebraska, and Missouri, is at or slightly above the national average, while South Dakota is far below average. New York has a very low activity rate (18.9 percent) while next door, Pennsylvania has a much higher rate of 25.6 percent.

Even in more active states, these numbers may look exceedingly low. If—at the very best—less than a third of adults get enough exercise, that's bad news. But take a few caveats into account before you go judging the entire country as a bunch of couch potatoes. These are broad recommendations, and don't necessarily reflect everyone's health needs; people who are injured, disabled, or chronically ill, for example, aren't going to be able to go for hour-long runs every week, and they shouldn't.

Plus, there are some gaps in this data. The survey relates specifically to leisure time exercise, meaning that it can't reflect the full activity levels of people who have physically demanding jobs. If you're a door-to-door canvasser who walks all day, a yoga teacher, or a UPS driver who lugs boxes around, the bulk of your physical activity might not happen in your down time, but that doesn't mean you're not exercising. Commute time doesn't count as leisure, either, so the results don't factor in the exercise you might get if you bike or walk to work each day.

That said, there is plenty of other evidence that Americans spend too much time in their cars and in front of screens and not enough time moving. The problem is just much worse in Indiana than in Colorado.

[h/t Thrillist]

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More Than 75 Percent of Americans Don't Exercise Enough
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If you're like the majority of Americans, you're probably not exercising enough. According to a new study from the Centers for Disease Control and Prevention (CDC) reported by Fortune, less than a quarter of U.S. adults met the recommended amount of weekly aerobic and muscle-building activity between 2010 and 2015 [PDF].

The leisure exercise guidelines the CDC referenced were set in 2008: They suggest that adults complete at least 150 minutes of "moderate-intensity aerobic physical activity" a week, 75 minutes of "vigorous-intensity aerobic physical activity," or a mix of the above. Just 22.9 percent of adults ages 18 to 64 met this criteria. For men, the national average was 27.2 percent, and for women, it was 18.7 percent.

The CDC study, which was released June 28, also broke down exercise habits by state. Colorado came in as the most active state, with 32.5 percent of residents meeting the exercise standards—nearly 10 percent more than the national average. People in Mississippi were the least likely to work out enough, with the average there coming out to just 13.5 percent.

Map of how much people exercise.
CDC

While the CDC's study only looked at leisure exercise, it's possible the results would have been different if it had also looked at the physical labor we do for our jobs, or just the walks we take on our commutes. The CDC points out that people with physically demanding jobs or those who bike or walk to get around may be less likely to exercise in their free time, even if they're technically more active overall than the people who do.

No matter how you compare to the CDC's standards, it never hurts to find room in your schedule for more exercise. Not only does working out have physical health benefits, but it can improve your mental health as well by boosting your energy and helping you fight stress. Here are some tips for creating a fitness routine if you don't have one already.

[h/t Fortune]

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