Running gives you a lot of things: Stress relief, personal records, chafing—the list goes on. In fact, you can add “butter” to that list right now.
Running content creator Libby Cope has gone viral not for her pace or mileage, but for what she makes along the way. Her video showing how she churns butter on a train run has racked over one million likes across Instagram and TikTok. Let’s dig into the science of how this works, and why this is my favorite kind of running influencer content right now.
How to churn butter while you run
In her viral videos, Cope pours heavy cream and salt into double-bagged Ziplocs, tucks the squishy dairy parcels into her running vest alongside her boyfriend, and heads out onto the trails. By the time they’re done, so is the butter. They spread it on sandwich bread and eat it right there. So, how crazy is this feat exactly?
As the Center for Dairy Research explains it, this sort of makes perfect sense. Milk is an emulsion—a mixture of fat and water molecules that don’t naturally want to coexist. Left alone long enough, milk will begin to separate, with the fattier molecules floating to the top. That fatty layer skimmed from the surface is cream. And cream, it turns out, is one aggressive trail run away from becoming butter.
When cream is agitated—like with all the shaking that comes with a trail run—the fat molecules suspended within it start bumping into each other. Eventually, they begin to stick together, clustering into larger and larger clumps and pushing the remaining liquid (buttermilk) to the outside. What’s left in the center of that shake-up should be butter.
The key variables are time and intensity of agitation. A casual stroll probably won’t cut it, since the movement needs to be sustained and vigorous enough to keep the fat molecules colliding. A trail run, with its constant up-and-down impact, its jostling vest pockets, and its 30-plus minutes of continuous movement, is more likely to get the job done. Essentially, your body is doing the work a wooden churn or a stand mixer would otherwise do.
There are plenty of other variables to consider, of course. Cold temperatures can slow the process, while too much heat will melt the whole production. Quality and amount of ingredients, the intensity of the run, and the weather outside all play a role in refining this run-churn process.
Cope’s videos aren’t the only examples of runners using their workout to make food. Running influencer TrailswithZach posted a tutorial last fall of how he makes chocolate ice cream while running, garnering over 137 thousand likes. Here’s another example from runner Irene Choi, who took things in a more creative direction with a corn juice honey butter recipe.
Why this social media trend matters (beyond the butter)
At a time when the online running community feels plagued by unrealistic expectations, this micro-movement is a breath of fresh air. It could be easy to write all of this off as a quirky internet moment, but there’s a deeper takeaway here. Cope told Runner’s World that the experience has been a grounding reminder of why she runs in the first place, and all the joy it brings her.
That’s the part that sticks, much like butter on bread. Online running culture gets daunting and discouraging, with all the pressure to buy the right shoes, post the fastest times, sign up for all the trendiest races, and so on. Churning butter while you run is a joyful reminder that running can also be playful and weird. Even if you don’t get down and dirty with buttercream yourself (something I have zero plans to do), these videos are a great way to reflect on why you run in the first place.
