I don't know about livestock, but growing your own veggies is WAY more efficient than getting them from agribusiness, and the veggies are far more nutritious if you use sound organic practices. I grow them on my parking strip on a small city lot, using homemade compost and home mixed organic fertilizer from bulk materials purchased once a year on the way to a climb. I just walk out of my front door and harvest. I gather about half the seeds I need from my plants.
No pesticides or oil based fertilizers. Total recycling. It doesn't get more efficient than that.
Quick - make a spreadsheet with all the vegetable products you consume in a year and tell me what % of them you grew yourself. How much of the bread you ate came from your own hand-raised wheat? How much coffee did you shade-grow?