There is some truth to that, and poor people are in a depressed economy most of the time. The wealthy who are fat, do not know how to quit eating the wrong things.
The smaller percentage amount may have either thyroid issues, health issues, or other things affecting weight.
Proteins like meat, etc are more expensive than carbs like bread. Balance and restraint are the key.
I think the man who ate at McDonalds for 90 days and lost weight proved that by his portions and choices.
And who's to blame for that in children, wait ... its on the tip of my tongue ... I can see it in my mind's eye .... Ummm, OH YES, PARENTS [or in a lot of cases, PARENT] !!!
Go for Mickey D's every night, KFC, pizza, soda, etc.
They'd be better off eating their peas ...