IPC's Nuts is tipped to win the circulation war, beating Emap's Zoo by about 90,000 copies. The rivals' circulations are expected to be 290,000 and 200,000 copies respectively.
In response, Emap is planning to relaunch Zoo with more pages and increased sports coverage.
The weekly titles are said to have added as much as 2m copy sales a month to the men's market, doubling its size from 1.8m to around 3.5m in six months.
The success of the titles has prompted H Bauer to enter the market with Cut, which will appear next month, while Richard Desmond, owner of Express Newspapers, has announced the launch of men's weekly KO!.
The weeklies' popularity is likely to have a negative effect on the men's monthly magazines. Loaded, which celebrated its 10th anniversary earlier this year, is expected to lose around 10% of its sales and Maxim is set for similar losses.
FHM, which was the UK's best selling monthly magazine with a circulation of just over 600,000 copies, is thought to have minimised its losses to around 4%.
Men's upmarket magazines such as Arena, GQ and Esquire are thought to be unaffected by the weeklies' surge.
Tim McCloskey, the press director at OMD, said: "This is good news for the men's market, whether we like the products or not. It is bringing young male consumers into the printed market, which can only be a good thing."
The losses at FHM have prompted some analysts to claim Conde Nast's Glamour could overtake the Emap title as the UK's number one consumer monthly. Glamour is expected to hit the 600,000-copy mark on Thursday, making it the first women's monthly to reach this figure.
The success of Glamour's handbag format has been picked up across the industry, with the likes of Cosmopolitan, Marie Claire and, last week, Elle all introducing smaller versions.
McCloskey added: "Glamour shows what can be done if you get the product right. It has managed to make a big footprint in the sector, drawing in younger readers from the teen market as well as older readers, something that Cosmopolitan could never really do."
The teen market is set to experience another bad period. Teenage girls are turning to adult magazines such as Glamour and are spending their money on other products such as mobile phones.
Sales of music magazines are expected to remain steady, with the likes of the NME, Mojo, Uncut and The Word doing relatively well because of aggressive marketing. Q is set for a fall but has just relaunched.
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