Your post got me thinking annbee as my husband was never really into fitness, although he is attending gym twice per week or so, he is jogging with me from time to time, but he never really got into this lifestyle as much as I did or other guys that I knew. As we get more and more into men's behavior, it may have to do with their need to dominate. My husband for example is a CEO for a pretty big company, he has both money and status. He is pretty handsome as well, so even though he never really took special care of his body he is feeling superior towards his peers in other areas, so he doesn't have to work out to prove himself as what he has is enough. I don't think this is the case with your husband as you told us, that he is not really getting out of home much, but I think the whole purpose of men attending gym and building their dream body is to become a man of an higher value. What if you husband already thinks he has this "value" and he simply doesn't want to work out because he doesn't see any reason to?
Does he play any video games or is he rich? He must have some areas, where he is superior and that may simple be enough for him.
I actually feel great on low carb diet and ever since I have first tried it, I loved it. I felt more energetic and stronger.
My performance at gym was also much better than before and what's most important - I wasn't going hungry and I still kept losing fat, so I guess it really depends.
I'm an endomorph though - I gain fat very quickly and it's hard for me to lose it, even though I'm relatively fit now, not overweight at all. I just don't react good to carbohydrates I guess.
I even feel like my digestive system is working better when I'm on limited amount of carbs, so... stick to Carb Cycling, if that's what works for you :)