The agency was appointed after LA Fitness held chemistry meetings with a number of undisclosed agencies.
The agency will develop a national integrated campaign - it will be the biggest integrated activity undertaken by the brand - and is aimed at differentiating LA Fitness from competitors such as Holmes Place, Fitness First, Fitness Exchange and David Lloyd.
The brief asked for an idea to increase membership sales at its 65 clubs across the UK.
Marc Nohr, the Kitcatt Nohr managing partner, said: "Most fitness brands market themselves in the same way - using the same implausibly athletic, Lycra-clad models. LA Fitness has the appetite to do something different, which will make it stand out from the crowd and appeal to new members. We look forward to helping it do exactly that."
A spokesman for LA Fitness said: "We have huge ambitions for the brand, both in terms of growth in the number of clubs and increasing membership of existing clubs."
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