CHICAGO — Protein Bar, a fast-casual restaurant chain specializing in healthy, on-the-go options, plans to use a capital investment from Catterton Partners to foster expansion across the country. Terms of the transaction announced Oct. 3 were not disclosed.

Protein Bar has 12 restaurants located in Chicago and Washington, D.C., and has announced plans to expand to Denver. The restaurant offers such menu items as quinoa bowls, salads and protein drinks.

Catterton Partners, a private equity firm based in Greenwich, Conn., has worked with such restaurant concepts as Noodles & Co., Outback Steakhouse and P.F. Chang’s, said Matt Matros, founder of Protein Bar. Catterton Partners has more than $4 billion under active management focused on growing consumer companies.

“We are delighted to partner with Catterton, the leading private equity firm in consumer investing,” Mr. Matros said. “We believe our concept, which is focused on providing on-the-go consumers with healthy options that boast great quality and flavor, is primed for growth.”

Mr. Matros founded Protein Bar in Chicago in 2009 after changing his diet and losing 60 lbs. He was an Ernst & Young Entrepreneur of the Year finalist in 2013 and one of Crain’s Chicago Business’ “40 Under 40” in 2012.

“We are excited about our investment in Protein Bar, a truly unique concept that capitalizes on two major restaurant trends: great tasting food and healthy, on-the-go options, all at an attractive price point,” said Scott A. Dahnke, co-managing partner of Catterton Partners. “With Catterton’s significant experience in helping to grow differentiated restaurant concepts and health-conscious brands, we believe Protein Bar is a perfect fit for the type of value we bring to our investments.”