The Manchester agency will handle PR and drive consumer awareness of the brand .
Marsh, 37, came to fame in the reality TV show Essex Wives in 2002 and went on to compete in Celebrity Big Brother.
In 2009 she underwent an incredible body transformation and went on to win the International Natural Bodybuilding Federation Championships in 2012.
This led her to launch a personal range of lifestyle and weight management supplements for men and women.
JAMpr will be kicking off with a PR drive for the brand’s sleep aid supplement, SLEEPEX and the HEBEX skin supplement, along with launching the recently developed OMG Protein Bars.
Marsh said: “JAM really understood the brand and our proposition so this feels like the perfect fit.
“The team really impressed us with its proven track record, delivering results with engaging, creative ideas and innovative campaigns.
“We were very much attracted to the team’s strategic approach, forward planning, its wealth of media contacts and overall enthusiasm for the products and JST Jodie brand.”
Jaime Gee, MD at JAM, added: “The team is incredibly excited to be working with JST Jodie.
“It’s a great brand offering quality products. Our experience with consumer campaigns makes us a great fit for the brand.”