Nonsense. Good, nutritional food is cheaper than the food people get fat on.
Poor people get fat for the same reasons everyone else does: because they're lazy and impulsive -- lacking in self-discipline. And the very fact that anybody can become not only overweight but actually obese regardless of income is a miracle of modern, petroleum-fueled capitalism.
Blaming so-called poverty for fatness would have been laughed at by anybody living during the past 10,000 years. "Imagine that: fat poor people!"
It's a perfect example of blindness to the incredible prosperity the author writes about.
This is all obviously extremely hypothetical to you; you have zero interaction with poor people, don’t you?