The problem is that for a lot of poorer communities where obesity is most rampant, there is no "grocery store to buy some vegetables or other healthy ingredient

The problem is that for a lot of poorer communities where obesity is most rampant, there is no "grocery store to buy some vegetables or other healthy ingredients" anywhere nearby and owning a car is not a given. So yes, making good choices is important, and most posters on HN are lucky enough to have healthy options easily accessible to them. But a lot of people, even in the US, do not have realistic healthy options available to them.