Private equity firm North Castle Partners is buying weight-loss company Jenny Craig to merge it with Curves International Inc. 

Jenny Craig operates a branded weight-loss program that includes coaching and food. Terms of the deal were not disclosed.

Greenwich, Conn.-based North Castle focuses on health, wellness and active living companies. In September 2012, the firm bought Curves, a chain of fitness studios for women.

North Castle plans to combine the two companies, but the two brands will continue to operate separately. After the deal closes, Monty Sharma, the CEO of Curves, will become the CEO of the combined business.

North Castle purchased Jenny Craig from Nestle (SIX: NESN), which paid about $600 million for the company in 2006.

The deal comes as Nestlé looks to sell some of its non-core brands.

Before Nestlé's ownership, Jenny Craig was owned by private equity firms MidOcean Partners and ACI Capital.

Those firms bought a majority stake in the company — known for its celebrity endorsers such as singer Mariah Carey and actress Carrie Fisher (pictured) — from founders, Jenny Craig and her husband, Sid, in 2002 for $115 million.