there's really no winning when your girlfriend says "i'm fat. i can't eat any more carbs." it's a trick statement. this is not one of those times where "agree with whatever she says" works. so what are you supposed to do? as a sensitive and caring guy? first, quickly change the subject; "was that a window breaking in the basement?!" -- and then, if you're like me, you invent some low carb dinners. such as this roasted pepper stuffed with onions, mushrooms, carrots, celery in a nest of brussel sprouts and lightly vinegared, spinach with a dab of vegan soy cheese. (it really wanted some plumb tomatoes, but i didn't have any.) then you make her one to take to work so when people say "what are you eating?" she can say "a low carb roasted pepper, stuffed with vegetables. my boyfriend made it for me." -- they get points for that kind of thing.