Sure it is nice to carry around huge packs of fresh vegetables and some beef in order to prepare a proper dish. However, it takes up space and moreover lots of mass in your backpack.
Also, a pound of butter may be highly efficient in terms of energy/mass ratio, however nobody want's to live of that stuff. Consider carbs, proteins and vitamins as well please.
We all want to remain healthy, especially if we are on our great outdoor adventure tours. So what is an effective selection of groceries for a prolonged weekend trekking trip?