Do Obese people use more health services? I'm not sure about that.
I see lots of emaciated people with pretty severe health problems. In fact, if you look at long term health figures, being overweight generally leads to greater health and less medical expenditure than being underweight. So do we charge the underweight too? Should models be surcharged for insurance?
The question is...how do you know someone is obese thru bad lifestyle or thru bad genes or thru disease? Some patients have thyroid issues that lead to obesity. Some people have need for medications that can cause obesity (antipsychotics, for example). Some patients probably have gut flora that is wrong and leads to obesity - this is a pretty promising angle in modern obesity science.
Obesity tends to skew toward the more healthy people, to be honest, except for T2 Diabetes - and frankly, most of the type 2 diabetes patients cannot reduce their weight - they would not be "medically judged" to be able to lose weight. Its really hard to do that when you have a massive amount of insulin in your system from diabetes, which is an anabolic hormone, and the treatment for it is.. give more of this hormone that makes you gain weight.
Heart failure paitents are often obese.. but I've diuresed 40 lbs of water off some of those.. so I'm not sure we can classify them as "medically judged" obese.