Since this is one of the most common questions I get, I took a moment to snap a picture of my setup on a recent grocery run.
In my panniers I have about 35 lbs of groceries, including frozen items and almond milk. Since I don’t eat meat I can’t attest to hauling home any steaks etc, but if it’s hot out or I have longer than a 10-15 minute ride home, I pop cold items into an insulated bag inside my pannier. I usually disperse the weight on both sides but with the weight behind you, it doesn’t affect the handling of the bike all that much.
If I wanted to haul more home (or were going on tour), I could add a bag to the top of my rear rack, a frame pack, and front panniers. For groceries however, I find that just two panniers at a time has me spending less on groceries and wasting less food, while paying more attention to what I eat and thus eating better as a result.
Also, I cheat. I order things like cat food and litter on Amazon, and sometimes bulk foods on groupon goods. I did that even when I had a car, because lugging things around using what little upper body strength I have is just not my jam. I also will go with friends to Trader Joes on the opposite side of town, because.. Have you been there? Then I need not explain. It’s Trader Joe’s. When the bike network here expands to reach it safely, and I get a trailer attachment for my bike, my life will be complete.