Maybe eventually eating plant matter won't be considered efficient either, what with the massive expenditure of fertilizer and ecological damage of pesticide and herbicide runoff.

We will need to figure out to bio-engineer edible plant matter as well. Then once we've mastered that, we can start bio-engineering ourselves to photosynthesize from the sun directly, to cut out all middlemen from the food chain. Then we can bio-engineer a vacuum-resistant carapace and launch ourselves toward the sun to exist as truly self-sufficient organisms. Then we blot out the sun with our flesh, and find some way to go to a different star.