The plans for a fresh brand identity, announced earlier this month, have been unveiled following a decline in sales at the food company in the first quarter of 2012, which it linked to a "continued weakness" in European sales.
It recorded net sales of $538m (£343m) in Europe for the quarter to 31 March, down 13.4% on the same quarter a year ago. Operating profit in Europe was also down 22.8% year on year, to $78m (£50m).
Kellogg said Twaddell has left to pursue other opportunities. He joined Kellogg in 1986 as a sales representative in Northern Ireland. He has held several sales and senior management roles at the company, and was named president of Kellogg Europe in 2010.
It is understood that his role, which includes European market-ing, is being overseen in the interim by Paul Norman, the senior vice-president and head of Kellogg International.
A source close to the business said that its bestselling brands in the region, Crunchy Nut and Special K, are under particular pressure due to unimpressive sales.
In addition, Kellogg faces increasing pressure from lobbyists in Europe over its marketing. Earlier this year, Kellogg was the subject of a complaint from the Children’s Food Campaign over its Krave cereal brand, although it was later cleared by the Advertising Standards Authority.
Kellogg recently paid $2.7bn for Procter & Gamble’s crisps brand Pringles and is now working on "extensive integration" of the business.
There has also been speculation that it will make a bid for United Biscuits, which owns McVitie's, Hula Hoops and Jaffa Cakes.