Libby Cope didn’t set out to revolutionize breakfast. She just wanted good butter.
First reported by Runner’s World, the 30-year-old Oregon-based running and outdoor content creator, along with her boyfriend Jacob Arnold, filled double-bagged Ziplocs 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 video has since pulled in more than 2 million views on TikTok and nearly 10 million on Instagram.
The idea started with fancy milk
The whole thing traces back to a bottle of cream-top milk from Alexandre Family Farms that Cope bought to put in her morning coffee. Arnold noticed how easily the thick liquid foamed when shaken and wondered out loud: could a run do the same thing?
The couple Googled it. They found that making butter in a bag was a known technique — something Cope vaguely remembered from high school — but no one seemed to have tried it by stuffing the bag in a running vest and going for a run. An AI overview said it was theoretically possible. They decided to find out for themselves.
“I actually prefer cooking outside over my own apartment,” Cope told Runner’s World. “I love cooking on a camp stove. It’s so much more exciting.”
Here’s why it works
Butter forms through agitation. 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. The body heat from their backs also helped. According to Scientific American, room-temperature cream turns to butter faster than cold cream because the molecules move more quickly at higher temperatures. Of course, if it gets too hot, everything melts — so this experiment probably wouldn’t work on a summer run.
Running for the butter
In their first attempt, Cope and Arnold each carried 32 ounces of heavy cream — two pints each — which Arnold later called “a little bit extreme.” They also stopped midway to cool their bags in a river, thinking body heat might be a problem. That actually slowed things down.
“It was probably 40 degrees outside, but there’s a lot of heat going on in the back,” said Cope.
Their second run produced better results. Cope credited higher-quality cream, a more strenuous trail, and warmer conditions. Arnold said the sweet spot is around 50 to 55 degrees Fahrenheit — warm enough for the fat molecules to move freely, cool enough that nothing melts.
The process takes roughly an hour of running, though both noted they kept stopping to check on their progress. Unlike fueling with running gels, this method requires a bit more patience — and a strong stomach for dairy.
The couple has since made more butter than they know what to do with. “We’ve consumed an alarming amount of dairy over the last week,” said Arnold. Cope added a less welcome side effect: “Yeah, I’m breaking out.”
Other runners are catching on
The video has already inspired a wave of copycat experiments. 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 too much. Cope has also discovered a runner named TrailswithZach, who has made chocolate ice cream and frosted lemonade during runs.
For the trail running crowd and marathon runners alike, the experiment is a reminder that running doesn’t always have to be about splits and finish times. Whether you’re dialling in your race-day nutrition or just out there for the joy of it, sometimes the best runs are the ones that end with something you made yourself.
“Sometimes it’s easy to forget what you’re doing it for, and it’s not for a bunch of medals and all that,” Cope said. “It’s just for the vibes. Just the butter.”
