Its a problem for sure. A large portion of the obese tend to be poor people who are working 40-80hours a week with half and hour to 2 hours commute every day who possibly have kids to take care of and may or may not be a single parent household, fast food isn't the cheapest option, but its the cheapest option they have time or the energy for. Also, since most fat food (and most other processed or prepared food sources) know how addictive high calorie and high salt foods can be they will happily take advantage of under educated and over stressed people by cramming as much as they can afford into their food. That of course doesn't apply to everyone and plenty of people who have no excuse are still fat but that applies to a rather large chunk of the overweight people. That also exposes a whole bunch of other issues that need to be addressed as well.