. She thinks that the more I run the more weight I will lose but she would prefer me to stay my 'cuddly' self. She has an issue with her own weight but can't find the motivation or inclination to do anything about it. Do you think that this could be the issue ?
Dave the ex spartan - what do I do if she won't let me dump her ?? 
I think you may have hit the nail right on the head there.
It's not at all unusual for partners of people trying to lose weight, stop smoking, drinking, etc., to not want them to succeed. They feel threatened by the change in their partner - particularly when it's a shared thing (both overweight/smokers/drinkers).
As you do lose weight, and your wife sees that you haven't run off with a skinny bird, she may come to feel less threatened by it.
Alternatively, run off with a skinny bird! 
(I think DtES and I went to the same marriage guidance college!)
Edited: 20/09/2012 at 15:13