Antidote won the business following a competitive pitch in March which included BBD Perfect Storm and Hey Human.
The first campaign is expected to break in the summer and will focus on a new product launch.
Henry Chilcott, managing director at Antidote, said: "Healthspan is the perfect client for us - an ambitious business with a great story to tell. We can’t wait to get started."
Antidote’s remit will cover television, print, radio, digital and direct and will work alongside MEC, Healthspan's media agency.
MEC was behind its last TV activity in 2013, which featured Felicity Kendal, star of BBC's The Good Life.
Chris Colmer, director of brand marketing at Healthspan, said: "We are entering an exciting period for Healthspan and in partnering with Antidote, who demonstrated insightful strategic thought and strong creative ideas, we believe we have a great opportunity to deliver excellent communications."
Earlier this month Antidote promoted Teddy Keen to the role of creative director. As deputy creative director, Keen was responsible for the agency’s recent ‘Fresh From Cinema’ Blinkbox campaign and the Royal 2015 summer campaign, ‘Like Nowhere Else’.