Editor's note: This story was originally published on USA TODAY in 2017. In the United States, a nation fatter than any other, running remains the most popular workout activity. That's according to a 2017 Fitbit analysis of fitness tracker user data. And if tied-up treadmills and new pandemic routines across the country are any indication, much of that running is long distance. Here’s the cruel catch, though: Running miles at a time doesn’t shed fat as efficiently as other forms of exercise.