What started as a curious experiment by an Oregon couple has become one of the quirkiest fitness trends on the internet: runners churning homemade butter simply by lacing up their shoes and hitting the trail with a bag of heavy cream tucked in their vest.
Libby Cope, a 30-year-old Oregon-based running and outdoor content creator, and her boyfriend Jacob Arnold, filled double-bagged zip-top bags with heavy cream and salt, tucked them inside their running vests, and headed out on a trail run. By the time they got back, they had homemade butter - which they spread on sandwich bread and ate on the spot.
The science behind it is straightforward. Cream is an emulsion - fat molecules suspended in liquid. When that emulsion gets shaken hard enough, the fat molecules start clinging together, pushing the liquid to the edges. What's left is butter. A trail run, with its constant jostling motion, is essentially a long, slow churning session. Body heat from their backs also helped.
Conditions matter. Arnold said the sweet spot is around 50 to 55 degrees Fahrenheit - warm enough for fat molecules to move freely, cool enough that nothing melts. The process takes roughly an hour of running. On their first attempt, Cope and Arnold each carried 32 ounces of heavy cream — two pints each - which Arnold later called "a little bit extreme." Their second run went more smoothly: better-quality cream, a more strenuous trail, and warmer conditions all helped.
The videos hit 2 million views on TikTok and 11 million on Instagram, and the idea spread worldwide. South Korea started hosting formal "Butter Run" events, with the trend emerging amid an unprecedented running boom there. According to a Gallup Korea survey, the country's running population is estimated at approximately 10 million as of 2025.
Copycats have been getting creative. Runner Irene Choi used the method to make corn juice honey butter. Lauren Lecompte tried it during a snowstorm but had to finish the job at home because the cold slowed the process. One runner named TrailswithZach has made chocolate ice cream and frosted lemonade during runs.
TikToker Jonny Arnott found his first try didn't pan out when commenters explained his local weather was too cold for effective butter clumping. He turned a problem into a solution and spiked his next carton of heavy cream with sugar before packing ice cubes around it - converting the challenge into an ice cream run instead.
For a running culture often obsessed with pace and performance data, the Butter Run is a refreshing detour. As Cope put it, sometimes the best runs end with something you made yourself.
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