Even though I am someone who struggles with his weight, I do not think that the food industry or restaurants should be held liable in any way.
First of all, this is not a situation like the one with cigarettes. It is not as if we don't know that eating too much makes us fat. It is not as if these industries are hiding the truth from us and trying to claim that overeating is healthy.
Given this, it is clearly our individual responsibility as to what we eat. The food industry and restaurants cannot force us to eat what we do not want to eat. We are responsible human beings who can decide for ourselves what we are going to eat.
Finally, think about the implications of holding these industries liable. We would essentially be giving the government the license to decide what we can and cannot eat. This is clearly not something that we want the government to be doing.
People need to be responsible for their own choices and actions. It is not the job of the food industry to keep us from eating badly. It is our own responsibility to monitor our health.