Private equity firm TSG Consumer Partners LLC has made an investment in Planet Fitness, a gym chain.

Planet Fitness is known for being a low-priced health club. The company is the brand partner for NBC show “The Biggest Loser” and has 618 locations with 3.8 million members. Memberships cost $10 per month.

TSG Consumer Partners, headquartered in San Francisco, has more than $2.9 billion in capital under management. The firm focuses on food, beverage, restaurant, beauty, personal care, retail and apparel sectors. Terms of the deal weren’t disclosed.