The move comes as part of an expected overhaul for the newspaper, owned by Guardian News & Media.
The newspaper will now have four weekly sections – news, sport, an expanded review section and the weekly Observer magazine. Business coverage will be embraced by the main section of the publication.
Observer Music Monthly, Sport Monthly and Observer Women will be dropped.
GNM has been carrying out a “strategic review” of its business and speculation built that it might even close The Observer. The company always denied this.
The newspaper will retain a core staff but many Observer journalists are to be integrated into editorial teams that work on The Guardian and its associated websites.
Editor John Mulholland is reported as saying: “The paper we have created as a result of this review will continue to uphold the proud tradition of Observer journalism. It will remain a serious, high quality, multi-section newspaper, independently edited and with its own distinctive voice.”
The newspaper posted a 6.59% to 385,617 rise in average net circulation for September compared to August – but was down 9.9% for the six month period April to September, year on year.
The GNM review has seen a restructuring of the commercial team and the planned departure of marketing director Marc Sands at the end of this year.