The correlation between poverty and obesity is more complicated than it first appears. "Poorer women are the most likely to be obese among all ethnicities. But there are a few counter-intuitive surprises here. The richest men were, overall, more likely to be obese than the poorest groups. The groups with the lowest rates of obesity were rich white women and poor black men. Obesity rises with income for black and Hispanic men, but it falls with income for black and Hispanic women. The relationship is clearly more complicated than 'a disease for poor people in a rich country.'"
This article in the Atlantic explains: http://www.theatlantic.com/business/archive/2013/11/the-messy-messy-relationship-between-income-and-race-and-obesity/281434/