The initiative, through Banks Hoggins O'Shea/FCB, is part of Weetabix's £7 million overhaul of its Alpen portfolio.
The revamp is a response to fundamental problems in the cereal sector, which has been seriously damaged by changing breakfast habits.
The advertising, which embraces everything from listings magazines to ticket barriers at railway stations, promotes the launch of Alpen Bars.
The products claim to have all the goodness of the main brand in an easy and convenient format. PHD is booking the media for the campaign, which aims to carry the message directly to young consumers in the major conurbations.
It is the latest stage of an attempt to reinvigorate Alpen, which began in May with the launch of a new TV campaign featuring the comedienne Arabella Weir and new packaging the following month.
The message is underlined in three executions that will appear in magazines such as GQ, Esquire, Glamour and Red. Each features a commuter trying to eat a bowl of Alpen in an impossible situation - a jam-packed lift, a jolting bus and a busy tube carriage.
The ads were written by Jason Cascarina, art directed by Andy Lennard and photographed by Kelvin Murray.
Ambient media will support the print work with rail ticket barriers carrying messages such as: "Alpen. Now available in rush hour."
Banks Hoggins picked up the Alpen account when Weetabix centralised its £16 million above-the-line business into the agency in November 2001.
Since then the company has expanded the Alpen range in an effort to steal market share from Jordan's, its main rival, and from supermarket own brands.
Alpen cereal bars were launched in June.