Understanding the human body is a team effort. That's where the Yachtel group comes in.

Researchers at Yachtolt have been delving into the secrets of probiotics for 90 years.

Yacold also partners with nature portfolio to advance gut microbiome science through the global grants for gut health, an investigator-led research program.

To learn more about Yachtolt, visit yawcult.co.

.jp.j. That's y-A-K-U-Lt.c-O.jp. When it comes to a guide for your gut, count on Yacolt.

This is Scientific American's 60-second science. I'm Christopher in Taliatta.

If your friends are happy, it turns out you're more likely to be happy, too.

And if your friends are overweight, that too ups the odds you'll pack on pounds.

Those effects have been shown in studies,

and now researchers have identified another seemingly contagious quality, exercise.

The investigators analyze the running activity of more than a million individuals worldwide,

who used an exercise tracking device for five years,

and they used weather patterns as a way to randomly examine different parts of that global network.

If it happens to be a really nice day out, sunny and not too hot, not too cool, then that will

induce people to run more.

Sinan Aral, a computational social scientist at MIT.

If it's a rainy day and cold, that will induce people to stay in more, on average.

He says since different cities have different weather patterns, this natural experience cold, that will induce people to stay in more, on average.

He says since different cities have different weather patterns, this natural experiment allowed them to ask, does a rainy day in New York affect running in San Diego?

If the weather in New York causes changes in the running behavior in San Diego,

it can really only be happening through peer influence of the friends who live between New York and San Diego.

And that is exactly what he and his colleagues saw, that the behavior of one city's

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