A new study from the Brookings Institution suggests that obesity costs the United States at least $215 billion dollars annually. Most of that comes from over $161 billion in increased health care costs (of which adult obesity increases health care costs by $147 billion and childhood obesity by $14.3 billion). However indirect costs of obesity also substantial. Though these are harder to estimate, one Brookings researcher suggests that productivity lost due to obesity-related illnesses could cost the American economy as much as $66 billion each year. Other costs are even more difficult to quantify, for instance larger people require larger vehicles increasing spending on gas and increasing the greenhouse gas emissions that cause global warming.
Finally, Brookings noted that obesity is positively and significantly correlated with lower rates of marriage, lower incomes, lower education rates and higher rates of poverty in women and with lower rates of marriage in men. Of course, correlation does not imply causation and it's quite possible that the same social conditions which cause these negative outcomes also cause higher rates of obesity.