Something that is making the round of the media lately is the findings of a December 2010 CDC report, Obesity and Socioeconomic Status in Adults: United States, 2005–2008 (PDF). The CDC looked at survey data from their National Health and Nutrition Examination Survey (NHANES) and found that the link between obesity and poverty was hardly clear-cut:
For more details, check out the report or other media takes (The Atlantic, Pew, and ConscienHealth).
Weight Maven is written by Beth Mazur. Beth believes that obesity is more symptom than cause and that the real problem is our Western diet -- especially sugar, refined grains, and industrial oils. Beth writes about nutrition, ancestral health, & food policy. And cats! 
That is an interesting breakdown of the figures. I can’t say I am all that surprised as all these kind of things seem to be less clear cut the closer you look at them.
A rather unscientific thought that springs to mind is that if you are poor it is more difficult to adjust to your weight in terms of things like clothes. I guess the wealthy can buy more expensive flattering clothes that make their weight less obvious? At least on a public level which could reinforce the poverty/obesity link in the public consciousness.
I think a contributing cause for the obesity:poverty::thin:wealthy link is the notion that eating healthy must be expensive and therefore thinness is a luxury for the rich. Fresh fruits, veggies and lean meats are usually more expensive than chips and hot pockets.
The key comparison would be between the younger, poorer, black and latino men who are thin versus the younger, poorer white men who are obese. Perhaps there is something in black and latino culture (like a social pressure) to be thin/muscular that drives it? Or perhaps it does boil down to different food choices? That’s the follow-up research I’d like to see.
I think the good food=expensive food is certainly true and may mean that wealthier people are better nourished. But when it comes to body weight there are plenty of good quality, expensive foods and drinks that can contribute to increased body weight. There is certainly social pressure amoung some groups of people but over the whole population that probably averages out.
“There is certainly social pressure amoung some groups of people but over the whole population that probably averages out.”
Except the very thing that makes this study interesting is that it empirically shows that it *doesn’t* even out. Poor white men get fat, while poor black and latino men get thin (the data even goes so far as to point out it is a statistically significant trend).
I really hope they do a follow-up study on this!