Sounds like a bunch of excuses by your husband to put you off asking for a "better" sex life. If you were 20lbs lighter with a perfect make up job, would it really be any different over the long term? I wonder if there is some other issues that are being swept away by coming up with yet another set of excuses?
For what it is worth, for me I don't really care if my w is overweight or not, rather I care how she feels about herself. The more she cares about herself, the better I feel about her and our relationship. As far as physical intamcy goes, in my ideal world I would only ask that my wife would desire to have a passionate relationship with me. I don't think I would even want to have a runway beautiful wife and sacrifice any amount of warmth and passion for "beauty". I bet most guys would feel the same.
Keep working out to make you feel good about yourself, but I doubt that it would make a big difference in your physical realtionship without getting to the bottom of what is the real issue with your h.