I remember getting McD's hamburgers and fries when I was a kid. They were a hamburger, not a Big Mac or even a Quarter Pounder. I am not sure they even had different sized fries. At best they had small and regular or some such.
The thing is food is cheap compared to other expenses. Giving someone a super sized order of fries does not cost that much compared to the price charged so McD's makes more money and the customer gets more food.
People do simply eat too much. Years ago we were planning a vacation at Disney World and I was reading a website about WDW. There was a discussion about fat adults and children at WDW. One lady stated that the parents of the fat kids should be arrested for child abuse which I thought was extreme.
I have noticed there are more fat kids in school today than when I was a kid so I understood a bit why the lady made the statement but still, I thought it was extreme.
Then we made the trip.

There were way to many fat adults and children. I do not mean they need to loose a few pounds fat. I mean morbidly obese fat. There was a family from the UK on one of the buses on day. The kid was fat. I noticed his swollen ankles and I caught my self wondering if the kid already had Congestive Heart Diseases.
I saw a morbidly obese man on a scooter. This guy was HUGE. He had just driven around the lake at EPCOT which I think is two miles. His morbidly obese daughter was huffing and puffing walking behind him on the scooter. She was in distress, out of breath and red faced. She was 13-14, had to be at least 250 pounds and was in no shape to be walking a couple of miles. Behind him, I saw his two sons, about 8-10 and already close to 200 pounds each, sharing a ride on a scooter which is a no no. They were zipping around people like they were pylons. The mother was just as huge and brought up the rear in a third scooter. Not sure why the poor daughter had to walk.
That family of five easily totaled 1,000 pounds. Some people have health problems which leads to added weight. I get that. But this family and others simply eat too much.
After I saw the family of five, I thought the lady who stated the parents of fat kids should be charged with child abuse may have been right.... Course that opens a Pandora's Box to which I have no good answer.
Later,
Dan