That Metrocard may be as good as a gym membership.

Researchers have determined that higher mass transit use is linked to lower obesity rates in counties across the country. When a mass transit system is "healthy" and operational, it promotes more walking and other health-promoting activity that driving does not.

"When someone rides a bus, they may begin their trip by walking from their home to a bus stop…then, they may still need to walk from a bus stop to their destination," said co-author of the study, Sheldon H. Jacobson.

The study, conducted by the University of Illinois at Urbana-Champaign, found that for each single percent increase of people riding mass transit, obesity rates dropped by 0.2%. This may not seem like a lot, but considering the amount of people who do take advantage of public transit, it’s a considerable statistic to note.

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The researchers of this study previously discovered that reduced driving, even by a mile, lead to a reduced body mass index (BMI).

If people choose driving over taking mass transit, "they might simply drive directly from their home to their destination and eliminate the walking portion of the trip," Jacobson said.