When it comes to issues surrounding public health, people can start out apathetic or hostile. Then, if the issue increases in frequency and becomes worse. Responses change, sympathy increases, this leads to action being demanded. Even if there was something that could be done about weight, the most important thing about the crisis is to keep fat people hated.
Health activists are shaping being fat as like the habit of smoking, so fat people can become the target of hate and stigma. More like the habit, rather than say people who have a disease. Which would mitigate against stigma, such as HIV/AIDS or mental health -as fatness has been modelled. The focus isn't dealing with obesity, they can't anyway, it is enabling certain people to draw scarce health funds towards useless, repetitive research and expensive treatments of a dubious ethical standard.
Not to say efficacy.
I also think society's overall inaction reflects the fact that a lot of the crisis is hype pure and simple. How can you act when there's little to act on, (or with)?
I can see that some people who are trying to take a more sympathetic and understanding line towards fatness are trying to frame it as addiction or a mental health issue. Apart from being wrong though, this is tiresome. You cannot weigh mental health anymore than you can weigh moral probity or the state of one's diet.