It's mostly about the drive through. Is it impossible to make drive through with food that isn't grossly terrible for you?

Doesn't that mean the cause is related to car culture (drive-thru) and processed foods, not just overeating?

I think you are reading too far into my McDonalds example. There are plenty of McDonalds without a drive through, who still overserve their customers. There are also plenty of people who are overweight just because they love to cook and eat tasty food (soul food!).

Why are chefs nearly always overweight? They work incredibly hard and tax their bodies for 10 hours a day. They aren't sitting in drive throughs. Maybe it has to do with the fact that they are around food all day and consume large quantities of it