Foster, who will report to managing director Jessica Burley, is Burger King North West Europe's senior marketing manager.
He has extensive experience of marketing FMCG goods, and will be tasked with strengthening the branding of the company's major titles, which include Cosmopolitan, Good Housekeeping, Esquire and Harper's Bazaar.
Burley said: "Bringing in an experienced marketeer will help us take the strength of our brands to the next level in terms of copy sales and stand out.
"Simon's experience in developing brand strategy and motivating consumer purchase will be invaluable in this highly competitive market."
Foster added: "I'm excited to be joining Jessica and her team working on such great brands. The category is facing a number of unique challenges at present, and I am looking forward to working with the team on the optimal strategy for the NatMag profile."
The company has also announced that Colette Harris will become the new print and editor for You & Your Wedding at the end of the month.
She is former editor of Emap's now defunct Health Plus, and will be taking over from Carole Hamilton.
Meribeth Parker, group publishing director for Nat Mag's wedding group, said: "You & Your Wedding is the bridal bible in the market place, and Colette's experience will make her an excellent addition to our team in this competitive specialist market."
You & Your Wedding has a circulation of 59,583.
The two new appointments follow the poaching by Nat Mags of Sian Rees, editor-in-chief of new projects for German publishing house Hubert Burda, to become the new editor of She magazine last month.
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