I wouldn't necessarily freely offer that information unless it was asked of me...nor would i dodge the question. Answer the question and see where it goes, but don't dwell on it. There's a reason why the past is called the past. You want your potential partner to see that you've dealt with what's happened in earlier relationships -- not that you're still hung up on it.
Dating is definitely a difficult thing. I've had my fair share of good and bad dates. What I've learned is that what you put out there is what you find. If you're expecting a potential partner to not be attracted to you because of your age or weight, that is what you dwell on during the date and that is what your date will see.
