True. This is something to worry about.
The decision is good and bad in my opinion. In one vein, physical activity and dietary guidance is the most proven long-term way to treat obesity, so this will put pressure on insurance companies to let doctors write prescriptions to see exercise and diet specialists. So this should end up increasing education and training in dietary and fitness for the general population, which is a huge inarguable benefit.
In another vein though, this will further monopolize control over the treatment of millions of people. I don't think it'll get to the point where random non-medical professionals get sued by medical organizations for giving obesity-treating advice, but who knows, dumber things have happened. Sane heads don't often prevail.
To all the people saying obesity is not a disease, kindly shut up until you actually work with this population directly. Yeah, yeah, we get it, they should just put the fork down or whatever. A "disease" isn't something that comes from lifestyle choices, right? -- except in the case of damn near every disease we have. Osteoperosis is from not consuming enough bone-building nutrients and not getting enough exercise - but that's a disease. People sometimes get cancer from working in improper working environments - but that's disease. Lifestyle choices can end up manifesting as diseases, they have no barring on whether or not something is classified as a disease.