Interesting topic. Personally, I think that obesity, the outward manifestation of excess weight, is a medical issue. The CAUSE and RESPONSE, however, could be moral or medical. The moral issue is very personal and individual - what each one of us feels, how the weight is emotionally handled, and what the weight means for us (creating additional "sins" such as jealousy, envy, lying to cover up bad habits, etc).
The crazy thing is, is that the secular world has pushed for acceptance and personalization of certain groups yet obesity remains the sole condition where shaming and discrimination is allowed and encouraged. Even smokers are separated as individuals from their smoking behaviors. No one on the outside is able to really know if the obesity is due to moral issues or medical. There are ways to address behaviors without shaming the entire person. When people have approached me with sincere concern for my health and/or well being because of destructive behaviors, it wasn't easy to swallow, but I appreciated the care. Unfortunately, overall judgment occurs way more often.
I personally have felt that my obesity is a moral issue. Overeating and taking poor care of the body given to me really gives me a lot of shame. And instead of being able to use that to get it under control, it only feeds my drive to eat. I was trying to explain this to my skinny husband who kept trying to compare weight loss with smoking which he quit cold turkey. I said, imagine if while you were going through withdrawals, everyone you know kept smoking around you. Your coworkers decided to Celebrate all the birthdays of the month by having a smoking party and on several occasions, others brought in their own cigarettes to the office because they didn't want them at the house. You were also invited to several dinner parties where the hosts would be highly disappointed if you did not have a smoke after dinner, even though they knew you are trying to quit. After all, one little one couldn't hurt, could it? In addition, even though you might have gotten through all of that without smoking, someone smells the smoke still lingering on your clothes and decides to make a derogatory comment about this to you. Then you go on vacation and even your spouse expects you to smoke because they don't have the same types at home and when will you ever get to try them again? This is how I feel all the time with food. It is such an uphill battle that I agree you can't understand unless you have been here. And I have learned that the heavier you get, the harder it gets to control and the more moral issue it becomes for me.