My boyfriend and I have been together for about 2.5 years and through that I have gone up a little, lost it, and then gone up a little again. My size hasn't really changed by my body composition did.
When we met I was a size 8-10 (4-6 US) and 130 pounds but still flabby...this time last year I was still the same size but 140 pounds and a lot more muscular. At THIS moment I am 146 pounds and while still muscular have some dratted wobbly bits going on there...thats what I get for moving in with him >.< lol.
He's been attracted to me through it all. Its more my sense of body loathing from time to time that gets to me than ever thinking he finds me ugly.
HOWEVER my boyfriend is 6'6 (I'm 5'6 lol) and when I met him weighed 190 pounds of lean, hard ripped muscle. It was very nice lol but not as nice as he himself is.
Anyway, he gained a little weight and then had a bike accident (was struck by a car riding to work) and hurt his neck. He couldn't ride, swim, run or do anything for about 10 months in which time he gained quite a bit. He was up around 245 pounds and wouldn't let me touch him because he felt so ugly and awful (and a serious bout of depression didn't help)
I was like...don't be silly! You're gorgeous! Because he IS. Even with weight on he's a physically gorgeous guy but that aside I loved him for HIM.
I can understand how men get frustrated with us when we don't believe their comments that we look good to them no matter the few extra kilos.
He's recently started to run and ride again and has already lost about 10 pounds (I so wish I could lose so quickly) and is gaining his self confidence back.
Fundementally if its a strong healthy relationship I find I love the person for the person, not the body. I do need some physical attraction there but by the time I am that deeply involved with someone they ARE still physically attractive to me because they're attractive emotionally and mentally