Tesco Diets is the third biggest weight loss service provider in the UK and Ireland, after Weight Watchers and Slimming World.
C&W’s consumer practice will help Tesco mount a fresh challenge to its competitors.
Tesco Diets head of marketing Catriona O’Brien said the business had ‘ambitious targets’.
C&W Consumer MD Rebecca Grant added that the agency planned to ‘galvanise a new generation of consumers to embrace a healthier lifestyle’.
There was no incumbent agency.