I disagree that fast food restaurants are responsible for obesity and other health related problems. One reason is that the restaurant only serves food. Another reason is health problems come from many different sources, and the last reason is you the person control what you eat.
First of all you can't blame a restaurant for your problem because they only serve the food. If you become obese it's probably due to the fact you already had an unhealthy lifestyle to begin with. Also it depends on how many fatty foods you eat.
Secondly, there is a list of unhealthy things in this world and one can't just be the blame for it. Everyone is different, and their bodies take in nutrients differently. Somebody could be the healthiest person alive, but that doesn't mean they're not up for a stroke.
Finally, you yourself make the decision. There might not even be a difference between home fried chicken or restaurant style chicken and fries. If you know that it's unhealthy to you, why eat it or at least limit the amount you eat.
I feel these are reasonable examples as to why you can't blame a restaurant for serving unhealthy foods or being linked completely to obesity. The restaurant simply sells home made food for people on the go. For every meal that a restaurant serves, you can get the same foods at home. Being unhealthy can be caused by a number of sources or bad genes. You decide what your body intakes and you are the only person responsible for it.