I am disabled - and I used to be overweight.
The reasons I have "reasonable adjustment" under the Equality Act at work is due to my disability, not being overweight. My job involves sitting at a PC all day so the fact that being overweight makes my feet and ankles hurt wasn't a huge deal.
However, because I knew there were issues I couldn't change but things I could - I decided to reduce my problems as much as I could by losing weight.
I still have a wonky spine, I still bruise at the drop of a hat, I still get spontaneously breaking of veins etc BUT I no longer have knee and ankle pain, I'm also 2 dress sizes smaller.
It is a pain in the arse really, I need to exercise 50 minutes a day for 6 days a week and watch my portion sizes. However, I think the benefits outweigh the problems. No longer do I sit on the sofa eating a bag of crisps and a load of chocolate in the evenings. Occasionally I do this, but not often.
It requires huge lifestyle changes - for instance the exercise means DH does most of the cooking and tidying in the evenings. It also requires a lot of motivation and will power on my part.
I'm still disabled but only now with the bits I can't change.
With obesity and even being in a crap relationship people often believe they can't make a difference - you can, but it's hard work and you have to train yourself out of bad habits and develop a whole set of new ones. Undoing habits of 40 years is TOUGH. It is also impossible to tell people how much better they will feel!
Oh, and a growing amount of literature studying people with gastric band surgery in the US shows that often, those treated, become addicted to something else after the surgery, so a significant proportion of obese people do have an addiction. This is being studied under "addictive personality" research.