Just because this guy's last girl friend weighed 90 lbs, doesn't mean that she was his preferred body type - It's possible that he prefers your body type and liked her "in spite of" her weight. Or maybe he is attracted to a wide range of body types. My husband has dated women of all sizes. He's a big guy, but very outgoing, and women are drawn to him because he's so friendly, soicable, funny and fun to be with. I've had women flirt openly with him in front of my face, I suppose because they think I couldn't possibly be "competition" for them - they're wrong.
I've dated thin guys and fat guys, short guys and tall guys, attractive guys and homely guys. I've always dated good guys who were attracted to me. Was my personality or my body their favorite part? I don't know, I never really dug that deeply, if I dug a guy and he dug me, that's all that really mattered. I did usually bring up weight issues fairly early in the relationship, because there are guys who only date women they are physically attracted to and if they're only attracted to a certain body type they need to know that my body type tends to do quite a bit of changing.
I never felt that anyone liked me "despite my size," because I always felt that dating is always a package deal - if you don't like something in the package - you can't assume you can fix it. Peope aren't houses, fixer-uppers never work in the real world. When I began dating my husband I was very clear that I did intend to try to lose weight, but that I couldn't guarantee it.
I actually felt very reassured that he had dated women of a wide range of sizes, because it reassured me that I didn't have to stress about how he would react to size changes as I lost weight. Knowing that his physical preferences are "flexible" was a load off my mind.
I always felt that most guys who dated larger women, liked them that way and were as likely or more likely to leave a woman over weight loss than other guys might leave a woman for weight gain. Interestingly in my own dating experience, the fat guys were most flexible they were less likely to have a rigid "type" , whereas the thin guys interested in me were mostly "want you fat" or "wish you were fatter" types.
I never knowingly seriously dated anyone who had a fat preference, because it was not my preference to stay fat. I say knowingly, because some guys will hide their preference for larger women probably because they're embarassed.
They can't hide it forever, though. A guy who sabotages seeminly intentionally your diet efforts at every turn, may have a fat-only attraction or he migfht be a control freak or might just be stupid about weight loss. I also think some guys are so focused on getting the date, they say whatever they need to, in order to get you to go out with them. I certainly had guys be more understanding of my weight loss intentions before we dated than afterward.
But I've also had guys say they were interested in things I liked and then after dating a while, you found out they really hate your interests, but they wanted you to like them anyway. Guys are just as insecure as girls. Maybe not about weight, but they have all sorts of other hangups.
Regardless, you can just learn more about him and see where things lead.