While buying all of your groceries at a store like Whole Foods could potentially break the bank (I love you, WF, and visit your establishment at least once a week, but you are crazy expensive), there are other, less costly options.
It seems an irresistibly good deal, our 99¢ soda or $1.50 loaf of bread. But these prices represent just a fraction of the true costs of getting that soda and bread into our shopping bags. We pay for the hidden costs of the corporate food supply chain in multiple ways, not all of them financially.
Our cultural attitudes about the use of our feet and our forks are ill-advised, but not crazy; they always made sense before. For most of human history, calories were relatively scarce and physical activity was unavoidable. Our prevailing inclinations are well-suited to that scenario.