Alastair Gammell will join the company in the New Year as head of legal and company secretary.
WeightWatchers.co.uk launched in July in the hope of mirroring the success of US parent company WeightWatchers.com. Both are completely separate companies to Weight Watchers International.
The legal appointment at WeightWatchers.co.uk comes as the young company prepares for an imminent launch in mainland Europe.
Gammell said: “I'm looking forward to taking on a senior position in a young, dynamic company with a valuable brand and a strong, established presence in the US.”
Gammell will report to WeightWatchers.com's general counsel and its UK general manager. He will be responsible for all legal matters and expects to focus on data protection, commercial transactions, intellectual property and e-commerce matters.
Gammell brings extensive e-commerce experience gained from his time at Premium TV, which runs the websites of 78 professional football clubs and is involved in the distribution of radio and television rights.