The Fastest-Growing Gym Franchise In America

Once a month, national gym chain Planet Fitness has a free pizza night.

So many members come in for these food-filled evenings that the health club franchise usually gives away 250,000 slices each time, for more than 3 million pieces a year. That's probably not surprising when you consider that Planet Fitness recently hit 5 million members and is now the fastest-growing gym chain in the U.S., according to co-founder and chief executive Chris Rondeau.