This is such a tough situation. Unfortunately, if he's really older and set in his ways, chances are he may never come around. My Dad isn't necessarily racist but he wouldn't want me to date outside my race. I'm pretty positive that he would never accept if I dated a black man. I say that with certainty because he has a hard time even accepting my boyfriend now, who although is white, we've been living together for two years and my Dad doesn't believe in people "shacking up" and the whole sex before marriage thing. It's a hard thing to go through and I'm sure this is what your girlfriend is feeling.
All you can do is decide if you two are truly in this for good. If this is just something you think is just for fun or a temporary thing, maybe you need to rethink things because it will only be hurting her relationship with her father. On the flipside, if you do truly love each other and plan on getting married and having a family someday, then you have every right to live your lives no matter how her dad feels. Hopefully he'd come around some day.
Perhaps you could make an attempt to talk to her dad. Give him a call and invite him out to dinner with the two of you. Maybe then you could introduce yourself formally and express your good intentions about his daughter. Let him know about the good things you have to bring to the table as far as a future with her. Let him know about your education, career, etc. so he can a positive sense of who you are as a person. Maybe just maybe he could see past your color and see who you are inside. All you can do is extend a hand and hope he'll be willing to respond in kind.
As far as helping your girlfriend feel better about her weight, it's best to just always reinforce how sexy and beautiful you think she is. It's really up to her to believe you or not.
