People have produced far more calories than required, through hand methods, for millennia. That's how cities and industrial society was able to develop. It has been by no means equal in all parts of the world.
Someone living on a tropical island surrounded by a reef might be able to gather all of the resources required to sustain life in a short amount of time. Someone living in the far north would have to struggle to do so. But I guess that's hunter-gatherer and not agriculture.
I saw a study once that showed the labor cost of producing a given amount of potatoes which was considered
enough for a family of four. To get the same caloric value of rice, six times more labor was required. The arrival of the potato in Europe helped to Spur the Industrial Revolution. I know from my own experiences that if I put 1/4 of my time into growing food, it would be vastly more than I could ever eat.
One of the worst calorie trades I know of is the harvest of fish from the ocean. On a worldwide basis, approximately one kilogram of diesel fuel is burned for every kilogram of landed fish. Of course there are many more calories in the diesel fuel. The guy paddling out to sea in his dugout canoe, doesn't contribute to that diesel burning. But there are boats running around the ocean chasing tuna, that burn 5 and 10 kg of fuel per kilogram of fish. Based on this knowledge, I think the most environmentally sensible fish to eat, would be those that are caught in inshore waters and the mouths of rivers, where it's done with minimal expenditure of petroleum. Farmed Fish like tilapia and other
vegetarian fish grown by tropical farmers are probably the most
sustainable fish of all.