Context could help you to manage the layout. In the past, i would use the Page manager of Chaos Tool Suite and Panels to control the layout but now i have completely move to the Context module. You can decide which regions should be hidden.
1. Download and enable the Context module.
4. Save the context and the regions should be disabled.
I have tried it on Omega theme but it does not work at all. However, when i apply it on the default Bartik theme, the Sidebar first could be hidden but not Header.
Reference: Drupal module – Context