Mum's Cinnamon Bread  

 

According to eqtraders, this food has a "duration index" of 120, which makes it much more long lasting than Iron Ration, which has index 25.

The "duration index" indicates, according to testing, that 1 index point makes the food/drink last 144 seconds if consumed naturally, i.e. without right-clicking it. This makes the Cinnamon Bread last almost 5 hours! Right-clicking the food cuts the duration in half. Furthermore, when tested back in 2003, Monks consumed food at half the rate, and being mounted tripled consumption. We also now have the Metabolism AA, which overall reduces consumption.