Like men, we women each have our own personal tastes. However, we are not nearly as hung up on appearances as you guys are. We are much, much more likely to look past a bad body and find the endearing, loveable man inside.
Yes, health is important, but size is not always the best indicator of health and fitness. We should all focus on eating well and getting plenty of exercise regardless of whether we intend to gain weight, lose weight, or maintain our weight.
My personal preference for a guy is this: I like men who are big and tall. My husband is 6' and weighs about 215 or so. He's strong and muscular, which I like, but he is also nice and cuddly, too. He has a perfect little belly (hint, a lot of women find a small belly on a man to be sexy), too. He is fit and healthy, but he is not a slave to his physical appearance, and that is appealing. I like feeling small standing beside him. That's what's attractive to me.
Oh, and I forgot -- you asked if there's a limit to what we would put up with. I would never leave my husband because of his physical appearance. His weight could go way up or way down, and he would still be the man I love. I might find myself less physically attracted to him were he to lose 50 pounds or gain a hundred, but he's still my man.
Slovenly dress and uncleanliness is far more off-putting to me than weight when it comes to the average guy you see in the store or at the gas station, btw.