Gower, who will start her new role on September 8, joins from Grazia magazine where she is currently consultant editor.
She replaces former editor Alison Pylkkanen, who has led the title for several years.
Prior to her most recent role Gower worked for titles including First, VIVA and SHE magazines.
"Mandie joins us with great credentials and a clear understanding of Zest and its readers," said Jessica Burley, National Magazine’s managing director, in a press release.
"She has an enormous amount of experience working across some of the UK's leading health and beauty titles and will be a major asset to Zest."
Finance reporter - property
