Going on a date when you are overweight, don't know if I should say something before the date

Supposed to go on a date, but I'm worried about my weight being an issue. I was supposed to travel up to meet her but she ended up not being able to meet me that day. So said she would make it up to me and make the effort to travel down to where I live. How could I bring it up into a conversation before we meet incase she changed her mind. I'm trying to lose weight but it's difficult. I just need some advice on what to do