Buzasi is joining the senior leadership team of WGSN Trends in the newly created role of global chief content officer, responsible for a network of 400 journalists.
Since its launch in 2011, HuffPost UK is now reaching around three million unique browsers, according to comScore, from a team of 25 journalists. Last month, Jimmy Maymann, chief executive of Huffington Post, said the UK operation was on track to turn its first profit this year.
Buzasi called the experience a "once-in-a-lifetime role" but said: "Now it is time for a new chapter and another amazing opportunity, and I couldn't be more excited about joining WGSN Trends to lead its world-class team of content experts and forecasters".
HuffPo’s executive editor, Stephen Hull, has been appointed editor in chief of Huffington Post UK following the exit of Buzasi.
Arianna Huffington, president of The Huffington Post Media Group, said: "I’m very grateful we had Carla for the birth of HuffPost UK. Her dedication and passion helped turn a hungry newborn into a precocious, award-winning 3-year-old.
"She also built a truly stellar team, including Stephen Hull and Poorna Bell, who are ready to move into leadership roles and take HuffPost UK to the next level.
"Stephen, who has been a fantastic leader of the news team, becomes our new editor in chief, and Poorna, who has done a wonderful job spearheading our lifestyle coverage, will be moving into the role of executive editor, as well as leading our efforts to bring the Thrive/Third Metric message to a global audience across all our editions."
WGSN Group provides strategic intelligence and trend forecasts for a global network of 75,000 paying users and generates revenues of about £70m.
Steve Newbold, global managing director at WGSN Trend, said: "Carla has clearly done an excellent job at Huffington Post and I am delighted she will now bring her leadership skills and considerable content expertise to our business.
"Our talented global creative teams at WGSN Trend provide unique information, detailed analysis and accurate forecasting services for our customers. Carla’s digital expertise, editorial vision and industry profile will add a further dimension to our global operations."