The agency will help Nuffield build awareness of the brand, which includes 65 fitness and well-being centres, as well as hospitals and corporate health services, across the country.
The7stars had previously worked on a project for the brand, but has not created any work for at least six months.
Sam Taylor, the brand and marketing communications director at Nuffield, said: "We have exciting plans for Nuf-field in 2013 and MediaCom are the perfect partner to ensure that our marketing communications will drive growth across all parts of our business."
In October, Nuffield kick-started a review of the advertising account for its gym business. It has most recently worked with Beta, which was handed the integrated business in October 2011. The review is ongoing.
This article was first published on campaignlive.co.uk